Assignment 5 Due: 11:59pm on Wednesday, March 5, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Conceptual Question 6.13 A hand presses down on the book in the figure. Part A Is the normal force of the table on the book larger than, smaller than, or equal to ? ANSWER: Correct mg Equal to Larger than Smaller than mg mg mg Problem 6.2 The three ropes in the figure are tied to a small, very light ring. Two of these ropes are anchored to walls at right angles with the tensions shown in the figure. Part A What is the magnitude of the tension in the third rope? Express your answer using two significant figures. ANSWER: Correct Part B What is the direction of the tension in the third rope? Express your answer using two significant figures. T  3 T3 = 94 N T  3 Typesetting math: 100% ANSWER: Correct The Normal Force When an object rests on a surface, there is always a force perpendicular to the surface; we call this the normal force, denoted by . The two questions to the right will explore the normal force. Part A A man attempts to pick up his suitcase of weight by pulling straight up on the handle. However, he is unable to lift the suitcase from the floor. Which statement about the magnitude of the normal force acting on the suitcase is true during the time that the man pulls upward on the suitcase? Hint 1. How to approach this problem First, identify the forces that act on the suitcase and draw a free-body diagram. Then use the fact that the suitcase is in equilibrium, , to examine how the forces acting on the suitcase relate to each other. Hint 2. Identify the correct free-body diagram Which of the figures represents the free-body diagram of the suitcase while the man is pulling on the handle with a force of magnitude ? = 58   below horizontal n ws n F = 0 fpull Typesetting math: 100% ANSWER: ANSWER: Correct Part B A B C D The magnitude of the normal force is equal to the magnitude of the weight of the suitcase. The magnitude of the normal force is equal to the magnitude of the weight of the suitcase minus the magnitude of the force of the pull. The magnitude of the normal force is equal to the sum of the magnitude of the force of the pull and the magnitude of the suitcase’s weight. The magnitude of the normal force is greater than the magnitude of the weight of the suitcase. Typesetting math: 100% Now assume that the man of weight is tired and decides to sit on his suitcase. Which statement about the magnitude of the normal force acting on the suitcase is true during the time that the man is sitting on the suitcase? Hint 1. Identify the correct free-body diagram. Which of the figures represents the free-body diagram while the man is sitting atop the suitcase? Here the vector labeled is a force that has the same magnitude as the man’s weight. ANSWER: wm n wm Typesetting math: 100% ANSWER: Correct Recognize that the normal force acting on an object is not always equal to the weight of that object. This is an important point to understand. Problem 6.5 A construction worker with a weight of 880 stands on a roof that is sloped at 18 . Part A What is the magnitude of the normal force of the roof on the worker? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct A B C D The magnitude of the normal force is equal to the magnitude of the suitcase’s weight. The magnitude of the normal force is equal to the magnitude of the suitcase’s weight minus the magnitude of the man’s weight. The magnitude of the normal force is equal to the sum of the magnitude of the man’s weight and the magnitude of the suitcase’s weight. The magnitude of the normal force is less than the magnitude of the suitcase’s weight. N  n = 840 N Typesetting math: 100% Problem 6.6 In each of the two free-body diagrams, the forces are acting on a 3.0 object. Part A For diagram , find the value of , the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B For diagram the part A, find the value of the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: kg ax x ax = -0.67 m s2 ay, y Typesetting math: 100% Correct Part C For diagram , find the value of , the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part D For diagram the part C, find the value of , the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: ay = 0 m s2 ax x ax = 0.67 m s2 ay y Typesetting math: 100% Correct Problem 6.7 In each of the two free-body diagrams, the forces are acting on a 3.0 object. Part A Find the value of , the component of the acceleration in diagram (a). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct ay = 0 m s2 kg ax x ax = 0.99 m s2 Typesetting math: 100% Part B Find the value of , the component of the acceleration in diagram (a). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C Find the value of , the component of the acceleration in diagram (b). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part D Find the value of , the component of the acceleration in diagram (b). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct ay y ay = 0 m s2 ax x ax = -0.18 m s2 ay y ay = 0 m s2 Typesetting math: 100% Problem 6.10 A horizontal rope is tied to a 53.0 box on frictionless ice. What is the tension in the rope if: Part A The box is at rest? Express your answer as an integer and include the appropriate units. ANSWER: Correct Part B The box moves at a steady = 4.80 ? Express your answer as an integer and include the appropriate units. ANSWER: Correct Part C The box = 4.80 and = 4.60 ? Express your answer to three significant figures and include the appropriate units. ANSWER: kg T = 0 N vx m/s T = 0 N vx m/s ax m/s2 Typesetting math: 100% Correct Problem 6.14 It takes the elevator in a skyscraper 4.5 to reach its cruising speed of 11 . A 60 passenger gets aboard on the ground floor. Part A What is the passenger’s weight before the elevator starts moving? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the passenger’s weight while the elevator is speeding up? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C What is the passenger’s weight after the elevator reaches its cruising speed? T = 244 N s m/s kg w = 590 N w = 730 N Typesetting math: 100% Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Block on an Incline A block lies on a plane raised an angle from the horizontal. Three forces act upon the block: , the force of gravity; , the normal force; and , the force of friction. The coefficient of friction is large enough to prevent the block from sliding . Part A Consider coordinate system a, with the x axis along the plane. Which forces lie along the axes? ANSWER: w = 590 N  F  w F n F  f Typesetting math: 100% Correct Part B Which forces lie along the axes of the coordinate system b, in which the y axis is vertical? ANSWER: Correct only only only and and and and and F  f F  n F  w F  f F  n F  f F  w F  n F w F  f F  n F w only only only and and and and and F  f F  n F  w F  f F  n F  f F  w F  n F w F  f F  n F w Typesetting math: 100% Usually the best advice is to choose coordinate system so that the acceleration of the system is directly along one of the coordinate axes. If the system isn’t accelerating, then you are better off choosing the coordinate system with the most vectors along the coordinate axes. But now you are going to ignore that advice. You will find the normal force, , using vertical coordinate system b. In these coordinates you will find the magnitude appearing in both the x and y equations, each multiplied by a trigonometric function. Part C Because the block is not moving, the sum of the y components of the forces acting on the block must be zero. Find an expression for the sum of the y components of the forces acting on the block, using coordinate system b. Express your answer in terms of some or all of the variables , , , and . Hint 1. Find the y component of Write an expression for , the y component of the force , using coordinate system b. Express your answer in terms of and . Hint 1. Some geometry help – a useful angle The smaller angle between and the y-axis is also , as shown in the figure. ANSWER: F  n Fn Fn Ff Fw  F n Fny F  n Fn  F  n  Typesetting math: 100% Hint 2. Find the y component of Write an expression for , the y component of the force , using coordinate system b. Express your answer in terms of and . Hint 1. Some geometry help – a useful angle The smaller angle between and the x-axis is also , as shown in the figure. ANSWER: ANSWER: Fny = Fncos() F f Ffy F f Ff  F  f  Ffy = Ffsin() Fy = 0 = Fncos() + Ffsin() − Fw Typesetting math: 100% Correct Part D Because the block is not moving, the sum of the x components of the forces acting on the block must be zero. Find an expression for the sum of the x components of the forces acting on the block, using coordinate system b. Express your answer in terms of some or all of the variables , , , and . Hint 1. Find the x component of Write an expression for , the x component of the force , using coordinate system b. Express your answer in terms of and . ANSWER: ANSWER: Correct Part E To find the magnitude of the normal force, you must express in terms of since is an unknown. Using the equations you found in the two previous parts, find an expression for involving and but not . Hint 1. How to approach the problem From your answers to the previous two parts you should have two force equations ( and ). Combine these equations to eliminate . The key is to multiply the Fn Ff Fw  F n Fnx F  n Fn  Fnx = −Fnsin() Fx = 0 = −Fnsin() + Ffcos() Fn Fw Ff Fn Fw  Ff Typesetting math: 100% Fy = 0 Fx = 0 Ff equation for the y components by and the equation for the x components by , then add or subtract the two equations to eliminate the term . An alternative motivation for the algebra is to eliminate the trig functions in front of by using the trig identity . At the very least this would result in an equation that is simple to solve for . ANSWER: Correct Congratulations on working this through. Now realize that in coordinate system a, which is aligned with the plane, the y-coordinate equation is , which leads immediately to the result obtained here for . CONCLUSION: A thoughtful examination of which coordinate system to choose can save a lot of algebra. Contact Forces Introduced Learning Goal: To introduce contact forces (normal and friction forces) and to understand that, except for friction forces under certain circumstances, these forces must be determined from: net Force = ma. Two solid objects cannot occupy the same space at the same time. Indeed, when the objects touch, they exert repulsive normal forces on each other, as well as frictional forces that resist their slipping relative to each other. These contact forces arise from a complex interplay between the electrostatic forces between the electrons and ions in the objects and the laws of quantum mechanics. As two surfaces are pushed together these forces increase exponentially over an atomic distance scale, easily becoming strong enough to distort the bulk material in the objects if they approach too close. In everyday experience, contact forces are limited by the deformation or acceleration of the objects, rather than by the fundamental interatomic forces. Hence, we can conclude the following: The magnitude of contact forces is determined by , that is, by the other forces on, and acceleration of, the contacting bodies. The only exception is that the frictional forces cannot exceed (although they can be smaller than this or even zero). Normal and friction forces Two types of contact forces operate in typical mechanics problems, the normal and frictional forces, usually designated by and (or , or something similar) respectively. These are the components of the overall contact force: perpendicular to and parallel to the plane of contact. Kinetic friction when surfaces slide cos  sin  Ff cos() sin() Fn sin2() + cos2 () = 1 Fn Fn = Fwcos() Fy = Fn − FW cos() = 0 Fn F = ma μn n f Ffric n f Typesetting math: 100% When one surface is sliding past the other, experiments show three things about the friction force (denoted ): The frictional force opposes the relative motion at the 1. point of contact, 2. is proportional to the normal force, and 3. the ratio of the magnitude of the frictional force to that of the normal force is fairly constant over a wide range of speeds. The constant of proportionality is called the coefficient of kinetic friction, often designated . As long as the sliding continues, the frictional force is then (valid when the surfaces slide by each other). Static friction when surfaces don’t slide When there is no relative motion of the surfaces, the frictional force can assume any value from zero up to a maximum , where is the coefficient of static friction. Invariably, is larger than , in agreement with the observation that when a force is large enough that something breaks loose and starts to slide, it often accelerates. The frictional force for surfaces with no relative motion is therefore (valid when the contacting surfaces have no relative motion). The actual magnitude and direction of the static friction force are such that it (together with other forces on the object) causes the object to remain motionless with respect to the contacting surface as long as the static friction force required does not exceed . The equation is valid only when the surfaces are on the verge of sliding. Part A When two objects slide by one another, which of the following statements about the force of friction between them, is true? ANSWER: Correct Part B fk fk μk fk = μkn μsn μs μs μk fs ! μsn μsn fs = μsn The frictional force is always equal to . The frictional force is always less than . The frictional force is determined by other forces on the objects so it can be either equal to or less than . μkn μkn μkn Typesetting math: 100% When two objects are in contact with no relative motion, which of the following statements about the frictional force between them, is true? ANSWER: Correct For static friction, the actual magnitude and direction of the friction force are such that it, together with any other forces present, will cause the object to have the observed acceleration. The magnitude of the force cannot exceed . If the magnitude of static friction needed to keep acceleration equal to zero exceeds , then the object will slide subject to the resistance of kinetic friction. Do not automatically assume that unless you are considering a situation in which the magnitude of the static friction force is as large as possible (i.e., when determining at what point an object will just begin to slip). Whether the actual magnitude of the friction force is 0, less than , or equal to depends on the magnitude of the other forces (if any) as well as the acceleration of the object through . Part C When a board with a box on it is slowly tilted to larger and larger angle, common experience shows that the box will at some point “break loose” and start to accelerate down the board. The box begins to slide once the component of gravity acting parallel to the board just begins to exceeds the maximum force of static friction. Which of the following is the most general explanation for why the box accelerates down the board? ANSWER: The frictional force is always equal to . The frictional force is always less than . The frictional force is determined by other forces on the objects so it can be either equal to or less than . μsn μsn μsn μsn μsn fs = μsn μsn μsn F = ma Fg The force of kinetic friction is smaller than that of maximum static friction, but remains the same. Once the box is moving, is smaller than the force of maximum static friction but larger than the force of kinetic friction. Once the box is moving, is larger than the force of maximum static friction. When the box is stationary, equals the force of static friction, but once the box starts moving, the sliding reduces the normal force, which in turn reduces the friction. Fg Fg Fg Fg Typesetting math: 100% Correct At the point when the box finally does “break loose,” you know that the component of the box’s weight that is parallel to the board just exceeds (i.e., this component of gravitational force on the box has just reached a magnitude such that the force of static friction, which has a maximum value of , can no longer oppose it.) For the box to then accelerate, there must be a net force on the box along the board. Thus, the component of the box’s weight parallel to the board must be greater than the force of kinetic friction. Therefore the force of kinetic friction must be less than the force of static friction which implies , as expected. Part D Consider a problem in which a car of mass is on a road tilted at an angle . The normal force Select the best answer. ANSWER: Correct The key point is that contact forces must be determined from Newton’s equation. In the problem described above, there is not enough information given to determine the normal force (e.g., the acceleration is unknown). Each of the answer options is valid under some conditions ( , the car is sliding down an icy incline, or the car is going around a banked turn), but in fact none is likely to be correct if there are other forces on the car or if the car is accelerating. Do not memorize values for the normal force valid in different problems–you must determine from . Problem 6.17 Bonnie and Clyde are sliding a 323 bank safe across the floor to their getaway car. The safe slides with a constant speed if Clyde pushes from behind with 375 of force while Bonnie pulls forward on a rope with 335 of force. μsn μsn μkn μsn μk < μs M  is found using n = Mg n = Mg cos() n = Mg cos() F  = Ma  = 0 n F = ma kg N N Typesetting math: 100% Part A What is the safe's coefficient of kinetic friction on the bank floor? ANSWER: Correct Problem 6.19 A crate is placed on a horizontal conveyor belt. The materials are such that and . Part A Draw a free-body diagram showing all the forces on the crate if the conveyer belt runs at constant speed. Draw the force vectors with their tails at the dot. The orientation of your vectors will be graded. The exact length of your vectors will not be graded but the relative length of one to the other will be graded. ANSWER: 0.224 10 kg μs = 0.5 μk = 0.3 Typesetting math: 100% Correct Part B Draw a free-body diagram showing all the forces on the crate if the conveyer belt is speeding up. Draw the force vectors with their tails at the dot. The orientation of your vectors will be graded. The exact length of your vectors will not be graded but the relative length of one to the other will be graded. ANSWER: Typesetting math: 100% Correct Part C What is the maximum acceleration the belt can have without the crate slipping? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct amax = 4.9 m s2 Typesetting math: 100% Problem 6.28 A 1100 steel beam is supported by two ropes. Part A What is the tension in rope 1? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the tension in rope 2? Express your answer to two significant figures and include the appropriate units. ANSWER: kg T1 = 7000 N Typesetting math: 100% Correct Problem 6.35 The position of a 1.4 mass is given by , where is in seconds. Part A What is the net horizontal force on the mass at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the net horizontal force on the mass at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 6.39 T2 = 4800 N kg x = (2t3 − 3t2 )m t t = 0 s F = -8.4 N t = 1 s F = 8.4 N Typesetting math: 100% A rifle with a barrel length of 61 fires a 8 bullet with a horizontal speed of 400 . The bullet strikes a block of wood and penetrates to a depth of 11 . Part A What resistive force (assumed to be constant) does the wood exert on the bullet? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How long does it take the bullet to come to rest after entering the wood? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 6.45 You and your friend Peter are putting new shingles on a roof pitched at 21 . You're sitting on the very top of the roof when Peter, who is at the edge of the roof directly below you, 5.0 away, asks you for the box of nails. Rather than carry the 2.0 box of nails down to Peter, you decide to give the box a push and have it slide down to him. Part A If the coefficient of kinetic friction between the box and the roof is 0.55, with what speed should you push the box to have it gently come to rest right at the edge of the roof? Express your answer to two significant figures and include the appropriate units. cm g m/s cm fk = 5800 N = 5.5×10−4 t s  m kg Typesetting math: 100% ANSWER: Correct Problem 6.54 The 2.0 wood box in the figure slides down a vertical wood wall while you push on it at a 45 angle. Part A What magnitude of force should you apply to cause the box to slide down at a constant speed? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct v = 3.9 ms kg  F = 23 N Typesetting math: 100% Score Summary: Your score on this assignment is 98.8%. You received 114.57 out of a possible total of 116 points. Typesetting math: 100%

Assignment 5 Due: 11:59pm on Wednesday, March 5, 2014 You will receive no credit for items you complete after the assignment is due. Grading Policy Conceptual Question 6.13 A hand presses down on the book in the figure. Part A Is the normal force of the table on the book larger than, smaller than, or equal to ? ANSWER: Correct mg Equal to Larger than Smaller than mg mg mg Problem 6.2 The three ropes in the figure are tied to a small, very light ring. Two of these ropes are anchored to walls at right angles with the tensions shown in the figure. Part A What is the magnitude of the tension in the third rope? Express your answer using two significant figures. ANSWER: Correct Part B What is the direction of the tension in the third rope? Express your answer using two significant figures. T  3 T3 = 94 N T  3 Typesetting math: 100% ANSWER: Correct The Normal Force When an object rests on a surface, there is always a force perpendicular to the surface; we call this the normal force, denoted by . The two questions to the right will explore the normal force. Part A A man attempts to pick up his suitcase of weight by pulling straight up on the handle. However, he is unable to lift the suitcase from the floor. Which statement about the magnitude of the normal force acting on the suitcase is true during the time that the man pulls upward on the suitcase? Hint 1. How to approach this problem First, identify the forces that act on the suitcase and draw a free-body diagram. Then use the fact that the suitcase is in equilibrium, , to examine how the forces acting on the suitcase relate to each other. Hint 2. Identify the correct free-body diagram Which of the figures represents the free-body diagram of the suitcase while the man is pulling on the handle with a force of magnitude ? = 58   below horizontal n ws n F = 0 fpull Typesetting math: 100% ANSWER: ANSWER: Correct Part B A B C D The magnitude of the normal force is equal to the magnitude of the weight of the suitcase. The magnitude of the normal force is equal to the magnitude of the weight of the suitcase minus the magnitude of the force of the pull. The magnitude of the normal force is equal to the sum of the magnitude of the force of the pull and the magnitude of the suitcase’s weight. The magnitude of the normal force is greater than the magnitude of the weight of the suitcase. Typesetting math: 100% Now assume that the man of weight is tired and decides to sit on his suitcase. Which statement about the magnitude of the normal force acting on the suitcase is true during the time that the man is sitting on the suitcase? Hint 1. Identify the correct free-body diagram. Which of the figures represents the free-body diagram while the man is sitting atop the suitcase? Here the vector labeled is a force that has the same magnitude as the man’s weight. ANSWER: wm n wm Typesetting math: 100% ANSWER: Correct Recognize that the normal force acting on an object is not always equal to the weight of that object. This is an important point to understand. Problem 6.5 A construction worker with a weight of 880 stands on a roof that is sloped at 18 . Part A What is the magnitude of the normal force of the roof on the worker? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct A B C D The magnitude of the normal force is equal to the magnitude of the suitcase’s weight. The magnitude of the normal force is equal to the magnitude of the suitcase’s weight minus the magnitude of the man’s weight. The magnitude of the normal force is equal to the sum of the magnitude of the man’s weight and the magnitude of the suitcase’s weight. The magnitude of the normal force is less than the magnitude of the suitcase’s weight. N  n = 840 N Typesetting math: 100% Problem 6.6 In each of the two free-body diagrams, the forces are acting on a 3.0 object. Part A For diagram , find the value of , the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B For diagram the part A, find the value of the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: kg ax x ax = -0.67 m s2 ay, y Typesetting math: 100% Correct Part C For diagram , find the value of , the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part D For diagram the part C, find the value of , the -component of the acceleration. Express your answer to two significant figures and include the appropriate units. ANSWER: ay = 0 m s2 ax x ax = 0.67 m s2 ay y Typesetting math: 100% Correct Problem 6.7 In each of the two free-body diagrams, the forces are acting on a 3.0 object. Part A Find the value of , the component of the acceleration in diagram (a). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct ay = 0 m s2 kg ax x ax = 0.99 m s2 Typesetting math: 100% Part B Find the value of , the component of the acceleration in diagram (a). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C Find the value of , the component of the acceleration in diagram (b). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part D Find the value of , the component of the acceleration in diagram (b). Express your answer to two significant figures and include the appropriate units. ANSWER: Correct ay y ay = 0 m s2 ax x ax = -0.18 m s2 ay y ay = 0 m s2 Typesetting math: 100% Problem 6.10 A horizontal rope is tied to a 53.0 box on frictionless ice. What is the tension in the rope if: Part A The box is at rest? Express your answer as an integer and include the appropriate units. ANSWER: Correct Part B The box moves at a steady = 4.80 ? Express your answer as an integer and include the appropriate units. ANSWER: Correct Part C The box = 4.80 and = 4.60 ? Express your answer to three significant figures and include the appropriate units. ANSWER: kg T = 0 N vx m/s T = 0 N vx m/s ax m/s2 Typesetting math: 100% Correct Problem 6.14 It takes the elevator in a skyscraper 4.5 to reach its cruising speed of 11 . A 60 passenger gets aboard on the ground floor. Part A What is the passenger’s weight before the elevator starts moving? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the passenger’s weight while the elevator is speeding up? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part C What is the passenger’s weight after the elevator reaches its cruising speed? T = 244 N s m/s kg w = 590 N w = 730 N Typesetting math: 100% Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Block on an Incline A block lies on a plane raised an angle from the horizontal. Three forces act upon the block: , the force of gravity; , the normal force; and , the force of friction. The coefficient of friction is large enough to prevent the block from sliding . Part A Consider coordinate system a, with the x axis along the plane. Which forces lie along the axes? ANSWER: w = 590 N  F  w F n F  f Typesetting math: 100% Correct Part B Which forces lie along the axes of the coordinate system b, in which the y axis is vertical? ANSWER: Correct only only only and and and and and F  f F  n F  w F  f F  n F  f F  w F  n F w F  f F  n F w only only only and and and and and F  f F  n F  w F  f F  n F  f F  w F  n F w F  f F  n F w Typesetting math: 100% Usually the best advice is to choose coordinate system so that the acceleration of the system is directly along one of the coordinate axes. If the system isn’t accelerating, then you are better off choosing the coordinate system with the most vectors along the coordinate axes. But now you are going to ignore that advice. You will find the normal force, , using vertical coordinate system b. In these coordinates you will find the magnitude appearing in both the x and y equations, each multiplied by a trigonometric function. Part C Because the block is not moving, the sum of the y components of the forces acting on the block must be zero. Find an expression for the sum of the y components of the forces acting on the block, using coordinate system b. Express your answer in terms of some or all of the variables , , , and . Hint 1. Find the y component of Write an expression for , the y component of the force , using coordinate system b. Express your answer in terms of and . Hint 1. Some geometry help – a useful angle The smaller angle between and the y-axis is also , as shown in the figure. ANSWER: F  n Fn Fn Ff Fw  F n Fny F  n Fn  F  n  Typesetting math: 100% Hint 2. Find the y component of Write an expression for , the y component of the force , using coordinate system b. Express your answer in terms of and . Hint 1. Some geometry help – a useful angle The smaller angle between and the x-axis is also , as shown in the figure. ANSWER: ANSWER: Fny = Fncos() F f Ffy F f Ff  F  f  Ffy = Ffsin() Fy = 0 = Fncos() + Ffsin() − Fw Typesetting math: 100% Correct Part D Because the block is not moving, the sum of the x components of the forces acting on the block must be zero. Find an expression for the sum of the x components of the forces acting on the block, using coordinate system b. Express your answer in terms of some or all of the variables , , , and . Hint 1. Find the x component of Write an expression for , the x component of the force , using coordinate system b. Express your answer in terms of and . ANSWER: ANSWER: Correct Part E To find the magnitude of the normal force, you must express in terms of since is an unknown. Using the equations you found in the two previous parts, find an expression for involving and but not . Hint 1. How to approach the problem From your answers to the previous two parts you should have two force equations ( and ). Combine these equations to eliminate . The key is to multiply the Fn Ff Fw  F n Fnx F  n Fn  Fnx = −Fnsin() Fx = 0 = −Fnsin() + Ffcos() Fn Fw Ff Fn Fw  Ff Typesetting math: 100% Fy = 0 Fx = 0 Ff equation for the y components by and the equation for the x components by , then add or subtract the two equations to eliminate the term . An alternative motivation for the algebra is to eliminate the trig functions in front of by using the trig identity . At the very least this would result in an equation that is simple to solve for . ANSWER: Correct Congratulations on working this through. Now realize that in coordinate system a, which is aligned with the plane, the y-coordinate equation is , which leads immediately to the result obtained here for . CONCLUSION: A thoughtful examination of which coordinate system to choose can save a lot of algebra. Contact Forces Introduced Learning Goal: To introduce contact forces (normal and friction forces) and to understand that, except for friction forces under certain circumstances, these forces must be determined from: net Force = ma. Two solid objects cannot occupy the same space at the same time. Indeed, when the objects touch, they exert repulsive normal forces on each other, as well as frictional forces that resist their slipping relative to each other. These contact forces arise from a complex interplay between the electrostatic forces between the electrons and ions in the objects and the laws of quantum mechanics. As two surfaces are pushed together these forces increase exponentially over an atomic distance scale, easily becoming strong enough to distort the bulk material in the objects if they approach too close. In everyday experience, contact forces are limited by the deformation or acceleration of the objects, rather than by the fundamental interatomic forces. Hence, we can conclude the following: The magnitude of contact forces is determined by , that is, by the other forces on, and acceleration of, the contacting bodies. The only exception is that the frictional forces cannot exceed (although they can be smaller than this or even zero). Normal and friction forces Two types of contact forces operate in typical mechanics problems, the normal and frictional forces, usually designated by and (or , or something similar) respectively. These are the components of the overall contact force: perpendicular to and parallel to the plane of contact. Kinetic friction when surfaces slide cos  sin  Ff cos() sin() Fn sin2() + cos2 () = 1 Fn Fn = Fwcos() Fy = Fn − FW cos() = 0 Fn F = ma μn n f Ffric n f Typesetting math: 100% When one surface is sliding past the other, experiments show three things about the friction force (denoted ): The frictional force opposes the relative motion at the 1. point of contact, 2. is proportional to the normal force, and 3. the ratio of the magnitude of the frictional force to that of the normal force is fairly constant over a wide range of speeds. The constant of proportionality is called the coefficient of kinetic friction, often designated . As long as the sliding continues, the frictional force is then (valid when the surfaces slide by each other). Static friction when surfaces don’t slide When there is no relative motion of the surfaces, the frictional force can assume any value from zero up to a maximum , where is the coefficient of static friction. Invariably, is larger than , in agreement with the observation that when a force is large enough that something breaks loose and starts to slide, it often accelerates. The frictional force for surfaces with no relative motion is therefore (valid when the contacting surfaces have no relative motion). The actual magnitude and direction of the static friction force are such that it (together with other forces on the object) causes the object to remain motionless with respect to the contacting surface as long as the static friction force required does not exceed . The equation is valid only when the surfaces are on the verge of sliding. Part A When two objects slide by one another, which of the following statements about the force of friction between them, is true? ANSWER: Correct Part B fk fk μk fk = μkn μsn μs μs μk fs ! μsn μsn fs = μsn The frictional force is always equal to . The frictional force is always less than . The frictional force is determined by other forces on the objects so it can be either equal to or less than . μkn μkn μkn Typesetting math: 100% When two objects are in contact with no relative motion, which of the following statements about the frictional force between them, is true? ANSWER: Correct For static friction, the actual magnitude and direction of the friction force are such that it, together with any other forces present, will cause the object to have the observed acceleration. The magnitude of the force cannot exceed . If the magnitude of static friction needed to keep acceleration equal to zero exceeds , then the object will slide subject to the resistance of kinetic friction. Do not automatically assume that unless you are considering a situation in which the magnitude of the static friction force is as large as possible (i.e., when determining at what point an object will just begin to slip). Whether the actual magnitude of the friction force is 0, less than , or equal to depends on the magnitude of the other forces (if any) as well as the acceleration of the object through . Part C When a board with a box on it is slowly tilted to larger and larger angle, common experience shows that the box will at some point “break loose” and start to accelerate down the board. The box begins to slide once the component of gravity acting parallel to the board just begins to exceeds the maximum force of static friction. Which of the following is the most general explanation for why the box accelerates down the board? ANSWER: The frictional force is always equal to . The frictional force is always less than . The frictional force is determined by other forces on the objects so it can be either equal to or less than . μsn μsn μsn μsn μsn fs = μsn μsn μsn F = ma Fg The force of kinetic friction is smaller than that of maximum static friction, but remains the same. Once the box is moving, is smaller than the force of maximum static friction but larger than the force of kinetic friction. Once the box is moving, is larger than the force of maximum static friction. When the box is stationary, equals the force of static friction, but once the box starts moving, the sliding reduces the normal force, which in turn reduces the friction. Fg Fg Fg Fg Typesetting math: 100% Correct At the point when the box finally does “break loose,” you know that the component of the box’s weight that is parallel to the board just exceeds (i.e., this component of gravitational force on the box has just reached a magnitude such that the force of static friction, which has a maximum value of , can no longer oppose it.) For the box to then accelerate, there must be a net force on the box along the board. Thus, the component of the box’s weight parallel to the board must be greater than the force of kinetic friction. Therefore the force of kinetic friction must be less than the force of static friction which implies , as expected. Part D Consider a problem in which a car of mass is on a road tilted at an angle . The normal force Select the best answer. ANSWER: Correct The key point is that contact forces must be determined from Newton’s equation. In the problem described above, there is not enough information given to determine the normal force (e.g., the acceleration is unknown). Each of the answer options is valid under some conditions ( , the car is sliding down an icy incline, or the car is going around a banked turn), but in fact none is likely to be correct if there are other forces on the car or if the car is accelerating. Do not memorize values for the normal force valid in different problems–you must determine from . Problem 6.17 Bonnie and Clyde are sliding a 323 bank safe across the floor to their getaway car. The safe slides with a constant speed if Clyde pushes from behind with 375 of force while Bonnie pulls forward on a rope with 335 of force. μsn μsn μkn μsn μk < μs M  is found using n = Mg n = Mg cos() n = Mg cos() F  = Ma  = 0 n F = ma kg N N Typesetting math: 100% Part A What is the safe's coefficient of kinetic friction on the bank floor? ANSWER: Correct Problem 6.19 A crate is placed on a horizontal conveyor belt. The materials are such that and . Part A Draw a free-body diagram showing all the forces on the crate if the conveyer belt runs at constant speed. Draw the force vectors with their tails at the dot. The orientation of your vectors will be graded. The exact length of your vectors will not be graded but the relative length of one to the other will be graded. ANSWER: 0.224 10 kg μs = 0.5 μk = 0.3 Typesetting math: 100% Correct Part B Draw a free-body diagram showing all the forces on the crate if the conveyer belt is speeding up. Draw the force vectors with their tails at the dot. The orientation of your vectors will be graded. The exact length of your vectors will not be graded but the relative length of one to the other will be graded. ANSWER: Typesetting math: 100% Correct Part C What is the maximum acceleration the belt can have without the crate slipping? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct amax = 4.9 m s2 Typesetting math: 100% Problem 6.28 A 1100 steel beam is supported by two ropes. Part A What is the tension in rope 1? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the tension in rope 2? Express your answer to two significant figures and include the appropriate units. ANSWER: kg T1 = 7000 N Typesetting math: 100% Correct Problem 6.35 The position of a 1.4 mass is given by , where is in seconds. Part A What is the net horizontal force on the mass at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B What is the net horizontal force on the mass at ? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 6.39 T2 = 4800 N kg x = (2t3 − 3t2 )m t t = 0 s F = -8.4 N t = 1 s F = 8.4 N Typesetting math: 100% A rifle with a barrel length of 61 fires a 8 bullet with a horizontal speed of 400 . The bullet strikes a block of wood and penetrates to a depth of 11 . Part A What resistive force (assumed to be constant) does the wood exert on the bullet? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Part B How long does it take the bullet to come to rest after entering the wood? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct Problem 6.45 You and your friend Peter are putting new shingles on a roof pitched at 21 . You're sitting on the very top of the roof when Peter, who is at the edge of the roof directly below you, 5.0 away, asks you for the box of nails. Rather than carry the 2.0 box of nails down to Peter, you decide to give the box a push and have it slide down to him. Part A If the coefficient of kinetic friction between the box and the roof is 0.55, with what speed should you push the box to have it gently come to rest right at the edge of the roof? Express your answer to two significant figures and include the appropriate units. cm g m/s cm fk = 5800 N = 5.5×10−4 t s  m kg Typesetting math: 100% ANSWER: Correct Problem 6.54 The 2.0 wood box in the figure slides down a vertical wood wall while you push on it at a 45 angle. Part A What magnitude of force should you apply to cause the box to slide down at a constant speed? Express your answer to two significant figures and include the appropriate units. ANSWER: Correct v = 3.9 ms kg  F = 23 N Typesetting math: 100% Score Summary: Your score on this assignment is 98.8%. You received 114.57 out of a possible total of 116 points. Typesetting math: 100%

Assignment 5 Due: 11:59pm on Wednesday, March 5, 2014 You … Read More...
What do Epicurus and Lucretius have to say about death? What do you think of their arguments?

What do Epicurus and Lucretius have to say about death? What do you think of their arguments?

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You will receive no credit for items you complete after the assignment is due. Grading Policy Exercise 2.5 Starting from the front door of your ranch house, you walk 60.0 due east to your windmill, and then you turn around and slowly walk 35.0 west to a bench where you sit and watch the sunrise. It takes you 27.0 to walk from your house to the windmill and then 49.0 to walk from the windmill to the bench. Part A For the entire trip from your front door to the bench, what is your average velocity? Express your answer with the appropriate units. ANSWER: Correct Part B For the entire trip from your front door to the bench, what is your average speed? Express your answer with the appropriate units. ANSWER: Correct Exercise 2.7 A car is stopped at a traffic light. It then travels along a straight road so that its distance from the light is given by , where = 2.40 and = 0.110 . = -0.329 average speed = 1.25 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 1 of 16 3/23/2015 11:12 AM Part A Calculate the average velocity of the car for the time interval = 0 to = 10.0 . ANSWER: Correct Part B Calculate the instantaneous velocity of the car at =0. ANSWER: Correct Part C Calculate the instantaneous velocity of the car at =5.00 . ANSWER: Correct Part D Calculate the instantaneous velocity of the car at =10.0 . ANSWER: Correct Part E How long after starting from rest is the car again at rest? ANSWER: = 13.0 = 0 = 15.8 = 15.0 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 2 of 16 3/23/2015 11:12 AM Correct Exercise 2.9 A ball moves in a straight line (the x-axis). The graph in the figure shows this ball’s velocity as a function of time. Part A What are the ball’s average velocity during the first 2.8 ? Express your answer using two significant figures. ANSWER: Answer Requested Part B What are the ball’s average speed during the first 2.8 ? Express your answer using two significant figures. ANSWER: Correct = 14.5 = 2.3 = 2.3 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 3 of 16 3/23/2015 11:12 AM Part C Suppose that the ball moved in such a way that the graph segment after 2.0 was -3.0 instead of +3.0 . Find the ball’s and average velocity during the first 2.8 in this case. Express your answer using two significant figures. ANSWER: All attempts used; correct answer displayed Part D Suppose that the ball moved in such a way that the graph segment after 2.0 was -3.0 instead of +3.0 . Find the ball’s average speed during the first 2.8 in this case. Express your answer using two significant figures. ANSWER: Correct Exercise 2.13 Part A The table shows test data for the Bugatti Veyron, the fastest car made. The car is moving in a straight line (the x-axis). Time 0 2.10 20.0 53.0 Speed 0 60.0 205 259 Calculate the car’s average acceleration (in ) between 0 and 2.1 . ANSWER: Correct Part B Calculate the car’s average acceleration (in ) between 2.1 and 20.0 . = 0.57 = 2.3 = 12.8 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 4 of 16 3/23/2015 11:12 AM ANSWER: Correct Part C Calculate the car’s average acceleration (in ) between 20.0 and 53 . ANSWER: Correct Exercise 2.19 An antelope moving with constant acceleration covers the distance 79.0 between two points in time 7.00 . Its speed as it passes the second point is 14.5 . Part A What is its speed at the first point? ANSWER: Correct Part B What is the acceleration? ANSWER: Correct Exercise 2.22 In the fastest measured tennis serve, the ball left the racquet at 73.14 . A served tennis ball is typically in contact with = 3.62 = 0.731 = 8.07 = 0.918 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 5 of 16 3/23/2015 11:12 AM the racquet for 27.0 and starts from rest. Assume constant acceleration. Part A What was the ball’s acceleration during this serve? ANSWER: Correct Part B How far did the ball travel during the serve? ANSWER: Correct Exercise 2.30 A cat walks in a straight line, which we shall call the x-axis with the positive direction to the right. As an observant physicist, you make measurements of this cat’s motion and construct a graph of the feline’s velocity as a function of time (the figure ). Part A Find the cat’s velocity at = 5.0 . Express your answer using two significant figures. ANSWER: = 2710 = 0.987 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 6 of 16 3/23/2015 11:12 AM Correct Part B Find the cat’s velocity at = 8.0 . Express your answer using two significant figures. ANSWER: Correct Part C What is the cat’s acceleration at ? Express your answer using two significant figures. ANSWER: Correct Part D What is the cat’s acceleration at ? Express your answer using two significant figures. ANSWER: Correct Part E What is the cat’s acceleration at ? Express your answer using two significant figures. ANSWER: = 1.3 = -2.7 = -1.3 = -1.3 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 7 of 16 3/23/2015 11:12 AM Correct Part F What distance does the cat move during the first 4.5 ? Express your answer using two significant figures. ANSWER: Correct Part G What distance does the cat move from to ? Express your answer using two significant figures. ANSWER: Correct Part H Sketch clear graph of the cat’s acceleration as function of time, assuming that the cat started at the origin. ANSWER: = -1.3 = 23 = 26 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 8 of 16 3/23/2015 11:12 AM Correct Part I Sketch clear graph of the cat’s position as function of time, assuming that the cat started at the origin. ANSWER: Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 9 of 16 3/23/2015 11:12 AM All attempts used; correct answer displayed Exercise 2.35 Part A If a flea can jump straight up to a height of 0.510 , what is its initial speed as it leaves the ground? ANSWER: Correct Part B How long is it in the air? ANSWER: Correct = 3.16 = 0.645 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 10 of 16 3/23/2015 11:12 AM Exercise 2.36 A small rock is thrown vertically upward with a speed of 18.0 from the edge of the roof of a 39.0 tall building. The rock doesn’t hit the building on its way back down and lands in the street below. Air resistance can be neglected. Part A What is the speed of the rock just before it hits the street? Express your answer with the appropriate units. ANSWER: Correct Part B How much time elapses from when the rock is thrown until it hits the street? Express your answer with the appropriate units. ANSWER: Correct Exercise 2.38 You throw a glob of putty straight up toward the ceiling, which is 3.00 above the point where the putty leaves your hand. The initial speed of the putty as it leaves your hand is 9.70 . Part A What is the speed of the putty just before it strikes the ceiling? Express your answer with the appropriate units. ANSWER: Correct Part B = 33.0 = 5.20 = 5.94 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 11 of 16 3/23/2015 11:12 AM How much time from when it leaves your hand does it take the putty to reach the ceiling? Express your answer with the appropriate units. ANSWER: Correct Exercise 3.1 A squirrel has x- and y-coordinates ( 1.2 , 3.3 ) at time and coordinates ( 5.3 , -0.80 ) at time = 2.6 . Part A For this time interval, find the x-component of the average velocity. Express your answer using two significant figures. ANSWER: Correct Part B For this time interval, find the y-component of the average velocity. Express your answer using two significant figures. ANSWER: Correct Part C Find the magnitude of the average velocity. Express your answer using two significant figures. ANSWER: = 0.384 = 1.6 = -1.6 = 2.2 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 12 of 16 3/23/2015 11:12 AM Correct Part D Find the direction of the average velocity. Express your answer using two significant figures. ANSWER: Correct Exercise 3.3 A web page designer creates an animation in which a dot on a computer screen has a position of 4.1 2.1 4.7 . Part A Find the average velocity of the dot between and . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part B Find the instantaneous velocity at . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part C = 45 below the x-axis = 4.2,4.7 = 0,4.7 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 13 of 16 3/23/2015 11:12 AM Find the instantaneous velocity at . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part D Find the instantaneous velocity at . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Exercise 3.5 A jet plane is flying at a constant altitude. At time it has components of velocity 89 , 108 . At time 32.5 the components are 165 , 37 . Part A For this time interval calculate the average acceleration. Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part B Find the magnitude of the average acceleration. Express your answer using two significant figures. ANSWER: = 4.2,4.7 = 8.4,4.7 = 2.3,-2.2 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 14 of 16 3/23/2015 11:12 AM Correct Part C Find the direction of the average acceleration (let the direction be the angle that the vector makes with the +x-axis, measured counterclockwise). ANSWER: Correct Exercise 3.4 The position of a squirrel running in a park is given by . Part A What is , the -component of the velocity of the squirrel, as function of time? ANSWER: Correct Part B What is , the y-component of the velocity of the squirrel, as function of time? ANSWER: = 3.2 = -43.1 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 15 of 16 3/23/2015 11:12 AM Correct Part C At 4.51 , how far is the squirrel from its initial position? Express your answer to three significant figures and include the appropriate units. ANSWER: All attempts used; correct answer displayed Part D At 4.51 , what is the magnitude of the squirrel’s velocity? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Part E At 4.51 , what is the direction (in degrees counterclockwise from +x-axis) of the squirrel’s velocity? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Score Summary: Your score on this assignment is 90.1%. You received 14.42 out of a possible total of 16 points. = 2.65 = 1.31 = 62.5 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 16 of 16 3/23/2015 11:12 AM

You will receive no credit for items you complete after the assignment is due. Grading Policy Exercise 2.5 Starting from the front door of your ranch house, you walk 60.0 due east to your windmill, and then you turn around and slowly walk 35.0 west to a bench where you sit and watch the sunrise. It takes you 27.0 to walk from your house to the windmill and then 49.0 to walk from the windmill to the bench. Part A For the entire trip from your front door to the bench, what is your average velocity? Express your answer with the appropriate units. ANSWER: Correct Part B For the entire trip from your front door to the bench, what is your average speed? Express your answer with the appropriate units. ANSWER: Correct Exercise 2.7 A car is stopped at a traffic light. It then travels along a straight road so that its distance from the light is given by , where = 2.40 and = 0.110 . = -0.329 average speed = 1.25 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 1 of 16 3/23/2015 11:12 AM Part A Calculate the average velocity of the car for the time interval = 0 to = 10.0 . ANSWER: Correct Part B Calculate the instantaneous velocity of the car at =0. ANSWER: Correct Part C Calculate the instantaneous velocity of the car at =5.00 . ANSWER: Correct Part D Calculate the instantaneous velocity of the car at =10.0 . ANSWER: Correct Part E How long after starting from rest is the car again at rest? ANSWER: = 13.0 = 0 = 15.8 = 15.0 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 2 of 16 3/23/2015 11:12 AM Correct Exercise 2.9 A ball moves in a straight line (the x-axis). The graph in the figure shows this ball’s velocity as a function of time. Part A What are the ball’s average velocity during the first 2.8 ? Express your answer using two significant figures. ANSWER: Answer Requested Part B What are the ball’s average speed during the first 2.8 ? Express your answer using two significant figures. ANSWER: Correct = 14.5 = 2.3 = 2.3 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 3 of 16 3/23/2015 11:12 AM Part C Suppose that the ball moved in such a way that the graph segment after 2.0 was -3.0 instead of +3.0 . Find the ball’s and average velocity during the first 2.8 in this case. Express your answer using two significant figures. ANSWER: All attempts used; correct answer displayed Part D Suppose that the ball moved in such a way that the graph segment after 2.0 was -3.0 instead of +3.0 . Find the ball’s average speed during the first 2.8 in this case. Express your answer using two significant figures. ANSWER: Correct Exercise 2.13 Part A The table shows test data for the Bugatti Veyron, the fastest car made. The car is moving in a straight line (the x-axis). Time 0 2.10 20.0 53.0 Speed 0 60.0 205 259 Calculate the car’s average acceleration (in ) between 0 and 2.1 . ANSWER: Correct Part B Calculate the car’s average acceleration (in ) between 2.1 and 20.0 . = 0.57 = 2.3 = 12.8 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 4 of 16 3/23/2015 11:12 AM ANSWER: Correct Part C Calculate the car’s average acceleration (in ) between 20.0 and 53 . ANSWER: Correct Exercise 2.19 An antelope moving with constant acceleration covers the distance 79.0 between two points in time 7.00 . Its speed as it passes the second point is 14.5 . Part A What is its speed at the first point? ANSWER: Correct Part B What is the acceleration? ANSWER: Correct Exercise 2.22 In the fastest measured tennis serve, the ball left the racquet at 73.14 . A served tennis ball is typically in contact with = 3.62 = 0.731 = 8.07 = 0.918 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 5 of 16 3/23/2015 11:12 AM the racquet for 27.0 and starts from rest. Assume constant acceleration. Part A What was the ball’s acceleration during this serve? ANSWER: Correct Part B How far did the ball travel during the serve? ANSWER: Correct Exercise 2.30 A cat walks in a straight line, which we shall call the x-axis with the positive direction to the right. As an observant physicist, you make measurements of this cat’s motion and construct a graph of the feline’s velocity as a function of time (the figure ). Part A Find the cat’s velocity at = 5.0 . Express your answer using two significant figures. ANSWER: = 2710 = 0.987 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 6 of 16 3/23/2015 11:12 AM Correct Part B Find the cat’s velocity at = 8.0 . Express your answer using two significant figures. ANSWER: Correct Part C What is the cat’s acceleration at ? Express your answer using two significant figures. ANSWER: Correct Part D What is the cat’s acceleration at ? Express your answer using two significant figures. ANSWER: Correct Part E What is the cat’s acceleration at ? Express your answer using two significant figures. ANSWER: = 1.3 = -2.7 = -1.3 = -1.3 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 7 of 16 3/23/2015 11:12 AM Correct Part F What distance does the cat move during the first 4.5 ? Express your answer using two significant figures. ANSWER: Correct Part G What distance does the cat move from to ? Express your answer using two significant figures. ANSWER: Correct Part H Sketch clear graph of the cat’s acceleration as function of time, assuming that the cat started at the origin. ANSWER: = -1.3 = 23 = 26 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 8 of 16 3/23/2015 11:12 AM Correct Part I Sketch clear graph of the cat’s position as function of time, assuming that the cat started at the origin. ANSWER: Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 9 of 16 3/23/2015 11:12 AM All attempts used; correct answer displayed Exercise 2.35 Part A If a flea can jump straight up to a height of 0.510 , what is its initial speed as it leaves the ground? ANSWER: Correct Part B How long is it in the air? ANSWER: Correct = 3.16 = 0.645 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 10 of 16 3/23/2015 11:12 AM Exercise 2.36 A small rock is thrown vertically upward with a speed of 18.0 from the edge of the roof of a 39.0 tall building. The rock doesn’t hit the building on its way back down and lands in the street below. Air resistance can be neglected. Part A What is the speed of the rock just before it hits the street? Express your answer with the appropriate units. ANSWER: Correct Part B How much time elapses from when the rock is thrown until it hits the street? Express your answer with the appropriate units. ANSWER: Correct Exercise 2.38 You throw a glob of putty straight up toward the ceiling, which is 3.00 above the point where the putty leaves your hand. The initial speed of the putty as it leaves your hand is 9.70 . Part A What is the speed of the putty just before it strikes the ceiling? Express your answer with the appropriate units. ANSWER: Correct Part B = 33.0 = 5.20 = 5.94 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 11 of 16 3/23/2015 11:12 AM How much time from when it leaves your hand does it take the putty to reach the ceiling? Express your answer with the appropriate units. ANSWER: Correct Exercise 3.1 A squirrel has x- and y-coordinates ( 1.2 , 3.3 ) at time and coordinates ( 5.3 , -0.80 ) at time = 2.6 . Part A For this time interval, find the x-component of the average velocity. Express your answer using two significant figures. ANSWER: Correct Part B For this time interval, find the y-component of the average velocity. Express your answer using two significant figures. ANSWER: Correct Part C Find the magnitude of the average velocity. Express your answer using two significant figures. ANSWER: = 0.384 = 1.6 = -1.6 = 2.2 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 12 of 16 3/23/2015 11:12 AM Correct Part D Find the direction of the average velocity. Express your answer using two significant figures. ANSWER: Correct Exercise 3.3 A web page designer creates an animation in which a dot on a computer screen has a position of 4.1 2.1 4.7 . Part A Find the average velocity of the dot between and . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part B Find the instantaneous velocity at . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part C = 45 below the x-axis = 4.2,4.7 = 0,4.7 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 13 of 16 3/23/2015 11:12 AM Find the instantaneous velocity at . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part D Find the instantaneous velocity at . Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Exercise 3.5 A jet plane is flying at a constant altitude. At time it has components of velocity 89 , 108 . At time 32.5 the components are 165 , 37 . Part A For this time interval calculate the average acceleration. Give your answer as a pair of components separated by a comma. For example, if you think the x component is 3 and the y component is 4, then you should enter 3,4. Express your answer using two significant figures. ANSWER: Correct Part B Find the magnitude of the average acceleration. Express your answer using two significant figures. ANSWER: = 4.2,4.7 = 8.4,4.7 = 2.3,-2.2 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 14 of 16 3/23/2015 11:12 AM Correct Part C Find the direction of the average acceleration (let the direction be the angle that the vector makes with the +x-axis, measured counterclockwise). ANSWER: Correct Exercise 3.4 The position of a squirrel running in a park is given by . Part A What is , the -component of the velocity of the squirrel, as function of time? ANSWER: Correct Part B What is , the y-component of the velocity of the squirrel, as function of time? ANSWER: = 3.2 = -43.1 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 15 of 16 3/23/2015 11:12 AM Correct Part C At 4.51 , how far is the squirrel from its initial position? Express your answer to three significant figures and include the appropriate units. ANSWER: All attempts used; correct answer displayed Part D At 4.51 , what is the magnitude of the squirrel’s velocity? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Part E At 4.51 , what is the direction (in degrees counterclockwise from +x-axis) of the squirrel’s velocity? Express your answer to three significant figures and include the appropriate units. ANSWER: Correct Score Summary: Your score on this assignment is 90.1%. You received 14.42 out of a possible total of 16 points. = 2.65 = 1.31 = 62.5 Week 2 https://session.masteringphysics.com/myct/assignmentPrintView?assignme… 16 of 16 3/23/2015 11:12 AM

Denial of service attacks are: Answers: A tactic where someone attempts to overload a company’s website to slow performance or even shut down a website Is an attack where hackers change critical passwords to deny access to legitimate users Attempts to shut down servers by interruption of power supplies All answers are correct

Denial of service attacks are: Answers: A tactic where someone attempts to overload a company’s website to slow performance or even shut down a website Is an attack where hackers change critical passwords to deny access to legitimate users Attempts to shut down servers by interruption of power supplies All answers are correct

Denial of service attacks are: Answers: A tactic where someone … Read More...
http://www.econlib.org/library/Smith/smWN1.html#B.I,%20Ch.1,%20Of%20the%20Division%20of%20Labor What does Smith mean by division of labor, and how does it affect production? A. He means that each person does their own work to benefit themselves by creating goods. This creates well-crafted goods. B. He argues that in order to become more efficient, we need to put everyone in the same workhouses and eliminate division. C. He says that the division of labor provides farmers with the opportunity to become involved in manufacturing. D. He means that each person makes one small part of a good very quickly, but this is bad for the quality of production overall. E. He means that by having each individual specialize in one thing, they can work together to create products more efficiently and effectively. Which of the following is NOT an example of the circumstances by which the division of labor improves efficiency? A. A doll-making company stops allowing each employee to make one whole doll each and instead appoints each employee to create one part of the doll. B. A family of rug makers buys a loom to speed up their production. C. A mechanic opens a new shop to be nearer to the market. D. A factory changes the responsibilities of its employees so that one group handles heavy boxes and the other group does precision sewing. E. A baker who used to make a dozen cookies at a time buys a giant mixer and oven that enable him to make 20 dozen cookies at a time. Considering the global system of states, what do you think the allegory of the pins has to offer? A. It suggests that there could be a natural harmony of interests among states because they can divide labor among themselves to the benefit of everyone. B. It suggests that states can never be secure enough to cooperate because every state is equally capable of producing the same things. C. It suggests that a central authority is necessary to help states cooperate, in the same way that a manager oversees operations at a factory. D. The allegory of the pins is a great way to think about how wars come about, because states won’t cooperate with each other like pin-makers do. E. The allegory of the pins shows us that there is no natural harmony of interests between states. Smith sees the development of industry, technology, and the division of labor as A. generally positive but not progressive. The lives of many people may improve, but the world will generally stay the same. B. generally positive and progressive. The world is improving because of these changes, and it will continue to improve. C. generally negative. The creation of new technologies and the division of labor are harmful to all humans, both the wealthy and the poor. D. generally negative. The creation of the division of labor only benefits the wealthy at the expense of the poor. E. both positive and negative. Smith thinks that technology hurts us, while the division of labor helps society progress and develop. http://www.youtube.com/watch?v=RUwS1uAdUcI What point is Hans Rosling trying to make when he describes the global health pre-test? A. He is trying to show how the average person has no idea of the true state of global health. B. He is trying to illustrate how we tend to carry around outdated notions about the state of global health. C. He is trying to make us see that the less-developed countries are far worse off than we ever thought. D. He is trying to drive home the idea that global health has not improved over time despite foreign aid and improvements in medicine. E. He is trying to warn us about the rapid growth in world population. Rosling shows us that we tend to think about global health in terms of “we and them.” Who are the “we” and who are the “them”? A. “We” refers to academics, students, and scholars; “them” refers to the uneducated. B. “We” refers to the average person; “them” refers to politicians and global leaders. C. “We” refers to the wealthy; “them” refers to the poor. D. “We” refers to the Western world; “them” refers to the Third World. E. “We” refers to students; “them” refers to professors. In the life expectancy and fertility rate demonstration, what do the statistics reveal? A. Over time, developed countries produced small families and long lives, whereas developing countries produced large families and short lives. B. The world today looks much like it did in 1962 despite our attempts to help poorer countries develop. C. All countries in the world, even the poorer ones, are trending toward longer lives and smaller families. D. Developed countries are trending toward smaller families but shorter lives. E. All countries tend to make gains and losses in fertility and lifespan, but in the long run there is no significant change. What point does Rosling make about life expectancy in Vietnam as compared to the United States? To what does he attribute the change? A. He indicates that economic change preceded social change. B. He suggests that markets and free trade resulted in the increase in life expectancy. C. He says that the data indicates that the Vietnam War contributed to the decrease in life expectancy during that time, but that it recovered shortly thereafter. D. He says that social change in Asia preceded economic change, and life expectancy in Vietnam increased despite the war. E. He indicates that Vietnam was equal to the United States in life expectancy before the war. According to Rosling, how are regional statistics about child survival rates and GDP potentially misleading? A. Countries have an incentive to lie about the actual survival rates because they want foreign assistance. B. Statistics for the individual countries in a region are often vastly different. C. Regional statistics give us a strong sense of how we can understand development within one region, but it does not allow us to compare across regions. D. The data available over time and from countries within regions is often poorly collected and incomplete. E. Child survival rates cannot be compared regionally, since each culture has a different sense of how important children are. What is Rosling’s main point about statistical databases? A. The data is available but not readily accessible, so we need to create networks to solve that problem. B. The data that comes from these databases is often flawed and unreliable. C. It doesn’t matter whether we have access to these databases because the data can’t be used in an interesting way. D. Statistics can’t tell us very much, but we should do our best to make use of the information we do have. E. The information that could be true is too hard to sort out from what isn’t true because we don’t know how strong the data really is. http://www.marxists.org/archive/lenin/works/1916/imp-hsc/ch10.htm#v22zz99h-298-GUESS Click the link at left to read Chapter 10 of Imperialism, The Highest Stage of Capitalism, then answer the questions below. According to Lenin, what is the fundamental source of a monopoly? A. It is a natural effect of human behavior. B. It is the result of governments and police systems. C. Its source is rooted in democracy. D. It comes from the concentration of production at a high stage. E. It is what follows a socialist system. What are the principal types or manifestations of monopoly capitalism? A. Monopolistic capitalist associations like cartels, syndicates and trusts; and monopolies as a result of colonial policy. B. Monopolization of raw materials and monopolization of finance capital. C. Monopolization of governing structures and monopolies of oligarchies. D. Monopolist capitalist associations like cartels, syndicates and trusts; and monopolies as a result of colonial policy AND monopolization of raw materials and monopolization of finance capital. E. Monopolization of raw materials and monopolization of finance capital AND monopolization of governing structures and monopolies of oligarchies. What is the definition of a rentier state according to Lenin? A. A state that colonizes other states. B. A state whose bourgeoisie live off the export of capital. C. A poor state. D. A wealthy state. E. A colonized state. Overall Lenin’s analysis of the state of capitalism is concerned with: A. The interactions between states. B. The interactions within states. C. The ownership of industry and organizations. D. The interactions within states AND the ownership of industry and organizations. E. All of these options. http://view.vzaar.com/1194665/flashplayer Watch the video at left, and then answer the questions below. The Marshall Plan was developed by the United States after World War II. What was its purpose? A. to feed the hungry of Europe B. to stem the spread of communism C. to maintain an American military presence in Europe D. to feed the hungry of Europe AND to stem the spread of communism E. to stem the spread of communism AND to maintain an American military presence in Europe What kind of aid was sent at first? A. foods, fertilizers, and machines for agriculture B. books, paper, and radios for education C. clothing, medical supplies, and construction equipment D. mostly cash in the form of loans and grants E. people with business expertise to help develop the economy What kind of aid did the United States send to Greece to help its farmers? A. tractors B. mules C. seeds D. fertilizer E. all of these options What was one way that the United States influenced public opinion in Italy during the elections described in the video? A. The United States provided significant food aid to Italy so that the Italians would be inclined to vote against the Communists. B. The Italians had been impressed by the strength and loyalty of the American soldiers, and were inclined to listen to them during the elections. C. There was a large number of young Italians who followed American fashion and culture. D. Italian immigrants in the United States wrote letters to their families in Italy urging them not to vote for Communists. E. The Greeks showed the Italians how much the Americans had helped them, warning that supporting a Communist candidate would mean sacrificing American aid. How did Pope Pius XII undermine the strength of the Communist Party in Italy? A. He encouraged Italians to go out and vote. B. He warned that the Communist Party would legalize abortion. C. He excommunicated many members of the Communist Party. D. He made a speech in support of capitalism. E. He declared that Communists should not be baptized. http://www.youtube.com/watch?v=KVhWqwnZ1eM Use the video at left to answer the questions below. Hans Rosling shares how his students discuss “we” versus “them.” To whom are his students referring? A. the United States and Mexico B. Christians and Muslims C. Democrats and Republicans D. Europe and Asia E. none of these options According to Rosling, what factors contribute to a better quality of life for people in developing countries? A. family planning B. soap and water C. investment D. vaccinations E. all of these options Using his data, Rosling demonstrates a great shift in Mexico. What change does his data demonstrate? A. a decrease in drug usage B. a decrease in the number of jobs available C. an increase in average life expenctancy D. an increase in the rate of violent crime E. all of these options Instead of “developing” and “developed,” Rosling divides countries into four categories. Which of the following is NOT one of them? A. high-income countries B. middle-income countries C. low-income countries D. no-income countries E. collapsing countries Rosling discusses the increased life expectancy in both China and the United States. How are the situations different? A. The U.S. and China are on different continents. B. The life expectancy in China rose much higher than it did in the U.S. C. China first expanded its life expectancy and then grew economically, whereas the U.S. did the reverse. D. Average income and life expectancy steadily increased in the U.S., but they steadily decreased in China. E. all of these options Rosling shows a chart that demonstrates the regional income distribution of the world from 1970 to 2015. During that time, what has happened in South and East Asia? A. Money has flowed out of Asia to developing countries in Africa. B. The average income of citizens of South and East Asia has increased over the last 30 years. C. The average income of citizens of South and East Asia has decreased over the last 30 years. D. The average income of citizens of South and East Asia has surpassed that of Europe and North America. E. There has been no change. Click here to access GapMinder, the data visualizer that Hans Rosling uses. In 2010, which of the following countries had both a higher per-capita GDP and a higher life expectancy than the United States? A. France B. Japan C. Denmark D. Singapore E. Kuwait http://www.garretthardinsociety.org/articles/art_tragedy_of_the_commons.html http://www.youtube.com/watch?v=8a4S23uXIcM The Tragedy of the Commons What is the rough definition of the “commons” given in the article? A. any private property on which others trespass B. behavior that everyone considers to be normal C. a cow that lives in a herd D. government-administered benefits, like unemployment or Social Security E. a shared resource What does Hardin mean by describing pollution as a reverse tragedy of the commons? A. Rather than causing a problem, it resolves a problem. B. Pollution costs us money rather than making us money. C. We are putting something into the commons rather than removing something from it. D. It starts at the other end of the biological pyramid. E. Humans see less of it as time goes on. Hardin says “the air and waters surrounding us cannot readily be fenced, and so the tragedy of the commons as a cesspool must be prevented by different means.” What are those means? A. establishing more international treaties to protect the environment B. using laws or taxes to make the polluter pay for pollution C. punishing consumers for generating waste D. raising awareness about environmental issues E. developing greener products Pacific Garbage Dump According to the news report, what percent of the Gyre is made of plastic? A. 50 percent B. 60 percent C. 70 percent D. 80 percent E. 90 percent Where does the majority of the plastic in the Gyre come from? A. barges that dump trash in the ocean B. storm drains from land C. people throwing litter off boats into the ocean D. remnants from movie sets filmed at sea E. fishing boats processing their catch What does Charles Moore mean by the “throwaway concept”? A. the habitual use of disposable plastic packaging B. the mistaken view that marine ecosystems are infinitely renewable C. a general lack of interest in recycling D. the willingness to discard effective but small-scale environmental policies in deference to broader E. people throwing away their lives in pursuit of money In what way does the Great Pacific Gyre represent issues like global warming a tragedy of the commons? A. because all the plastic trash in it comes from the United States B. because it kills the albatross and makes it impossible for them to reproduce C. surbecause the countries rounding the Pacific Ocean are polluting the water in a way that affects the quality of the resource for all, but no one is specifically accountable for it D. because it causes marine life to compete for increasingly scarce nutrients in the ocean E. because nations in the region all collectively agreed to dump their trash in the Pacific http://www.npr.org/news/specials/climate/video/ http://ngm.nationalgeographic.com/climateconnections/climate-map http://www.npr.org/news/specials/climate/video/wildchronicles.html Use the links provided at left to answer the questions below. Global Warming: It’s All About Carbon How does carbon give us fuel? A. When you burn things that contain carbon the bonds break, giving off energy. B. Burning things creates carbon out of other elements as a result of combustion. C. Carbon is created after oxygen and hydrogen get released. D. Carbon bonds are created thereby giving off energy. E. Carbon is made into fuel by refining oil. National Geographic Climate Map What geographic areas have seen the most significant changes in temperature? A. The African continent. B. The Pacific Ocean. C. The Atlantic Ocean. D. The Arctic Ocean. E. The Indian Ocean. Why does it matter that rain fall steadily rather than in downpours? A. For those countries accustomed to steady rain fall, downpours are actually more efficient ways to catch water. B. Downpours in regions accustomed to steady fall makes them more prone to flooding and damage. C. In general, as long as regions get either steady fall or downpours most things will stay the same. D. Downpours are always more beneficial to crop growth than steady rain. E. Steady rain is always more beneficial to crop growth than downpours. Climate Change Threatens Kona Coffee What is unique about the climate in Hawaii, making it a good place to grow coffee? A. The elevation is high, the nights are cool and the days are humid. B. The elevation is low, the nights are warm and the days are dry. C. The elevation is high, the nights are warm and the days are dry. D. The elevation is low, the nights are cool and the days are dry. E. The elevation is high, the nights are warm and the days are humid. What specific temperature pattern have experts noted about the region where Kona coffee is grown in Hawaii? A. There has been no significant change but the bean production has dropped. B. The nights have warmed up, even though the days have cooled. C. There has been an increase in bean production with the change in climate. D. The nights have cooled even more so than before. E. There has been universally hot days all the way around.

http://www.econlib.org/library/Smith/smWN1.html#B.I,%20Ch.1,%20Of%20the%20Division%20of%20Labor What does Smith mean by division of labor, and how does it affect production? A. He means that each person does their own work to benefit themselves by creating goods. This creates well-crafted goods. B. He argues that in order to become more efficient, we need to put everyone in the same workhouses and eliminate division. C. He says that the division of labor provides farmers with the opportunity to become involved in manufacturing. D. He means that each person makes one small part of a good very quickly, but this is bad for the quality of production overall. E. He means that by having each individual specialize in one thing, they can work together to create products more efficiently and effectively. Which of the following is NOT an example of the circumstances by which the division of labor improves efficiency? A. A doll-making company stops allowing each employee to make one whole doll each and instead appoints each employee to create one part of the doll. B. A family of rug makers buys a loom to speed up their production. C. A mechanic opens a new shop to be nearer to the market. D. A factory changes the responsibilities of its employees so that one group handles heavy boxes and the other group does precision sewing. E. A baker who used to make a dozen cookies at a time buys a giant mixer and oven that enable him to make 20 dozen cookies at a time. Considering the global system of states, what do you think the allegory of the pins has to offer? A. It suggests that there could be a natural harmony of interests among states because they can divide labor among themselves to the benefit of everyone. B. It suggests that states can never be secure enough to cooperate because every state is equally capable of producing the same things. C. It suggests that a central authority is necessary to help states cooperate, in the same way that a manager oversees operations at a factory. D. The allegory of the pins is a great way to think about how wars come about, because states won’t cooperate with each other like pin-makers do. E. The allegory of the pins shows us that there is no natural harmony of interests between states. Smith sees the development of industry, technology, and the division of labor as A. generally positive but not progressive. The lives of many people may improve, but the world will generally stay the same. B. generally positive and progressive. The world is improving because of these changes, and it will continue to improve. C. generally negative. The creation of new technologies and the division of labor are harmful to all humans, both the wealthy and the poor. D. generally negative. The creation of the division of labor only benefits the wealthy at the expense of the poor. E. both positive and negative. Smith thinks that technology hurts us, while the division of labor helps society progress and develop. http://www.youtube.com/watch?v=RUwS1uAdUcI What point is Hans Rosling trying to make when he describes the global health pre-test? A. He is trying to show how the average person has no idea of the true state of global health. B. He is trying to illustrate how we tend to carry around outdated notions about the state of global health. C. He is trying to make us see that the less-developed countries are far worse off than we ever thought. D. He is trying to drive home the idea that global health has not improved over time despite foreign aid and improvements in medicine. E. He is trying to warn us about the rapid growth in world population. Rosling shows us that we tend to think about global health in terms of “we and them.” Who are the “we” and who are the “them”? A. “We” refers to academics, students, and scholars; “them” refers to the uneducated. B. “We” refers to the average person; “them” refers to politicians and global leaders. C. “We” refers to the wealthy; “them” refers to the poor. D. “We” refers to the Western world; “them” refers to the Third World. E. “We” refers to students; “them” refers to professors. In the life expectancy and fertility rate demonstration, what do the statistics reveal? A. Over time, developed countries produced small families and long lives, whereas developing countries produced large families and short lives. B. The world today looks much like it did in 1962 despite our attempts to help poorer countries develop. C. All countries in the world, even the poorer ones, are trending toward longer lives and smaller families. D. Developed countries are trending toward smaller families but shorter lives. E. All countries tend to make gains and losses in fertility and lifespan, but in the long run there is no significant change. What point does Rosling make about life expectancy in Vietnam as compared to the United States? To what does he attribute the change? A. He indicates that economic change preceded social change. B. He suggests that markets and free trade resulted in the increase in life expectancy. C. He says that the data indicates that the Vietnam War contributed to the decrease in life expectancy during that time, but that it recovered shortly thereafter. D. He says that social change in Asia preceded economic change, and life expectancy in Vietnam increased despite the war. E. He indicates that Vietnam was equal to the United States in life expectancy before the war. According to Rosling, how are regional statistics about child survival rates and GDP potentially misleading? A. Countries have an incentive to lie about the actual survival rates because they want foreign assistance. B. Statistics for the individual countries in a region are often vastly different. C. Regional statistics give us a strong sense of how we can understand development within one region, but it does not allow us to compare across regions. D. The data available over time and from countries within regions is often poorly collected and incomplete. E. Child survival rates cannot be compared regionally, since each culture has a different sense of how important children are. What is Rosling’s main point about statistical databases? A. The data is available but not readily accessible, so we need to create networks to solve that problem. B. The data that comes from these databases is often flawed and unreliable. C. It doesn’t matter whether we have access to these databases because the data can’t be used in an interesting way. D. Statistics can’t tell us very much, but we should do our best to make use of the information we do have. E. The information that could be true is too hard to sort out from what isn’t true because we don’t know how strong the data really is. http://www.marxists.org/archive/lenin/works/1916/imp-hsc/ch10.htm#v22zz99h-298-GUESS Click the link at left to read Chapter 10 of Imperialism, The Highest Stage of Capitalism, then answer the questions below. According to Lenin, what is the fundamental source of a monopoly? A. It is a natural effect of human behavior. B. It is the result of governments and police systems. C. Its source is rooted in democracy. D. It comes from the concentration of production at a high stage. E. It is what follows a socialist system. What are the principal types or manifestations of monopoly capitalism? A. Monopolistic capitalist associations like cartels, syndicates and trusts; and monopolies as a result of colonial policy. B. Monopolization of raw materials and monopolization of finance capital. C. Monopolization of governing structures and monopolies of oligarchies. D. Monopolist capitalist associations like cartels, syndicates and trusts; and monopolies as a result of colonial policy AND monopolization of raw materials and monopolization of finance capital. E. Monopolization of raw materials and monopolization of finance capital AND monopolization of governing structures and monopolies of oligarchies. What is the definition of a rentier state according to Lenin? A. A state that colonizes other states. B. A state whose bourgeoisie live off the export of capital. C. A poor state. D. A wealthy state. E. A colonized state. Overall Lenin’s analysis of the state of capitalism is concerned with: A. The interactions between states. B. The interactions within states. C. The ownership of industry and organizations. D. The interactions within states AND the ownership of industry and organizations. E. All of these options. http://view.vzaar.com/1194665/flashplayer Watch the video at left, and then answer the questions below. The Marshall Plan was developed by the United States after World War II. What was its purpose? A. to feed the hungry of Europe B. to stem the spread of communism C. to maintain an American military presence in Europe D. to feed the hungry of Europe AND to stem the spread of communism E. to stem the spread of communism AND to maintain an American military presence in Europe What kind of aid was sent at first? A. foods, fertilizers, and machines for agriculture B. books, paper, and radios for education C. clothing, medical supplies, and construction equipment D. mostly cash in the form of loans and grants E. people with business expertise to help develop the economy What kind of aid did the United States send to Greece to help its farmers? A. tractors B. mules C. seeds D. fertilizer E. all of these options What was one way that the United States influenced public opinion in Italy during the elections described in the video? A. The United States provided significant food aid to Italy so that the Italians would be inclined to vote against the Communists. B. The Italians had been impressed by the strength and loyalty of the American soldiers, and were inclined to listen to them during the elections. C. There was a large number of young Italians who followed American fashion and culture. D. Italian immigrants in the United States wrote letters to their families in Italy urging them not to vote for Communists. E. The Greeks showed the Italians how much the Americans had helped them, warning that supporting a Communist candidate would mean sacrificing American aid. How did Pope Pius XII undermine the strength of the Communist Party in Italy? A. He encouraged Italians to go out and vote. B. He warned that the Communist Party would legalize abortion. C. He excommunicated many members of the Communist Party. D. He made a speech in support of capitalism. E. He declared that Communists should not be baptized. http://www.youtube.com/watch?v=KVhWqwnZ1eM Use the video at left to answer the questions below. Hans Rosling shares how his students discuss “we” versus “them.” To whom are his students referring? A. the United States and Mexico B. Christians and Muslims C. Democrats and Republicans D. Europe and Asia E. none of these options According to Rosling, what factors contribute to a better quality of life for people in developing countries? A. family planning B. soap and water C. investment D. vaccinations E. all of these options Using his data, Rosling demonstrates a great shift in Mexico. What change does his data demonstrate? A. a decrease in drug usage B. a decrease in the number of jobs available C. an increase in average life expenctancy D. an increase in the rate of violent crime E. all of these options Instead of “developing” and “developed,” Rosling divides countries into four categories. Which of the following is NOT one of them? A. high-income countries B. middle-income countries C. low-income countries D. no-income countries E. collapsing countries Rosling discusses the increased life expectancy in both China and the United States. How are the situations different? A. The U.S. and China are on different continents. B. The life expectancy in China rose much higher than it did in the U.S. C. China first expanded its life expectancy and then grew economically, whereas the U.S. did the reverse. D. Average income and life expectancy steadily increased in the U.S., but they steadily decreased in China. E. all of these options Rosling shows a chart that demonstrates the regional income distribution of the world from 1970 to 2015. During that time, what has happened in South and East Asia? A. Money has flowed out of Asia to developing countries in Africa. B. The average income of citizens of South and East Asia has increased over the last 30 years. C. The average income of citizens of South and East Asia has decreased over the last 30 years. D. The average income of citizens of South and East Asia has surpassed that of Europe and North America. E. There has been no change. Click here to access GapMinder, the data visualizer that Hans Rosling uses. In 2010, which of the following countries had both a higher per-capita GDP and a higher life expectancy than the United States? A. France B. Japan C. Denmark D. Singapore E. Kuwait http://www.garretthardinsociety.org/articles/art_tragedy_of_the_commons.html http://www.youtube.com/watch?v=8a4S23uXIcM The Tragedy of the Commons What is the rough definition of the “commons” given in the article? A. any private property on which others trespass B. behavior that everyone considers to be normal C. a cow that lives in a herd D. government-administered benefits, like unemployment or Social Security E. a shared resource What does Hardin mean by describing pollution as a reverse tragedy of the commons? A. Rather than causing a problem, it resolves a problem. B. Pollution costs us money rather than making us money. C. We are putting something into the commons rather than removing something from it. D. It starts at the other end of the biological pyramid. E. Humans see less of it as time goes on. Hardin says “the air and waters surrounding us cannot readily be fenced, and so the tragedy of the commons as a cesspool must be prevented by different means.” What are those means? A. establishing more international treaties to protect the environment B. using laws or taxes to make the polluter pay for pollution C. punishing consumers for generating waste D. raising awareness about environmental issues E. developing greener products Pacific Garbage Dump According to the news report, what percent of the Gyre is made of plastic? A. 50 percent B. 60 percent C. 70 percent D. 80 percent E. 90 percent Where does the majority of the plastic in the Gyre come from? A. barges that dump trash in the ocean B. storm drains from land C. people throwing litter off boats into the ocean D. remnants from movie sets filmed at sea E. fishing boats processing their catch What does Charles Moore mean by the “throwaway concept”? A. the habitual use of disposable plastic packaging B. the mistaken view that marine ecosystems are infinitely renewable C. a general lack of interest in recycling D. the willingness to discard effective but small-scale environmental policies in deference to broader E. people throwing away their lives in pursuit of money In what way does the Great Pacific Gyre represent issues like global warming a tragedy of the commons? A. because all the plastic trash in it comes from the United States B. because it kills the albatross and makes it impossible for them to reproduce C. surbecause the countries rounding the Pacific Ocean are polluting the water in a way that affects the quality of the resource for all, but no one is specifically accountable for it D. because it causes marine life to compete for increasingly scarce nutrients in the ocean E. because nations in the region all collectively agreed to dump their trash in the Pacific http://www.npr.org/news/specials/climate/video/ http://ngm.nationalgeographic.com/climateconnections/climate-map http://www.npr.org/news/specials/climate/video/wildchronicles.html Use the links provided at left to answer the questions below. Global Warming: It’s All About Carbon How does carbon give us fuel? A. When you burn things that contain carbon the bonds break, giving off energy. B. Burning things creates carbon out of other elements as a result of combustion. C. Carbon is created after oxygen and hydrogen get released. D. Carbon bonds are created thereby giving off energy. E. Carbon is made into fuel by refining oil. National Geographic Climate Map What geographic areas have seen the most significant changes in temperature? A. The African continent. B. The Pacific Ocean. C. The Atlantic Ocean. D. The Arctic Ocean. E. The Indian Ocean. Why does it matter that rain fall steadily rather than in downpours? A. For those countries accustomed to steady rain fall, downpours are actually more efficient ways to catch water. B. Downpours in regions accustomed to steady fall makes them more prone to flooding and damage. C. In general, as long as regions get either steady fall or downpours most things will stay the same. D. Downpours are always more beneficial to crop growth than steady rain. E. Steady rain is always more beneficial to crop growth than downpours. Climate Change Threatens Kona Coffee What is unique about the climate in Hawaii, making it a good place to grow coffee? A. The elevation is high, the nights are cool and the days are humid. B. The elevation is low, the nights are warm and the days are dry. C. The elevation is high, the nights are warm and the days are dry. D. The elevation is low, the nights are cool and the days are dry. E. The elevation is high, the nights are warm and the days are humid. What specific temperature pattern have experts noted about the region where Kona coffee is grown in Hawaii? A. There has been no significant change but the bean production has dropped. B. The nights have warmed up, even though the days have cooled. C. There has been an increase in bean production with the change in climate. D. The nights have cooled even more so than before. E. There has been universally hot days all the way around.

http://www.econlib.org/library/Smith/smWN1.html#B.I,%20Ch.1,%20Of%20the%20Division%20of%20Labor What does Smith mean by division of labor, and … Read More...
A factor that positively affected the state of women’s health care is: Question 3 options: the entry of women into the workforce during World War II Political attempts to control the distribution of information about reproductive options the treatment of menopause as an “illness” the different treatments for men and women suffering from heart disease

A factor that positively affected the state of women’s health care is: Question 3 options: the entry of women into the workforce during World War II Political attempts to control the distribution of information about reproductive options the treatment of menopause as an “illness” the different treatments for men and women suffering from heart disease

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Objective: Persuade readers that they should fear a threat of your choosing, real or fabricated. Due Date: Wednesday, November 18th Length: 4-5 pages Format: typed, double-spaced, standard font and margins For this essay, you will be putting together all the aspects of argument that we have been learning about over the last few weeks. You will be using those elements to convince your readers that some issue of your choosing is a threat to them. This issue can be a real threat that you believe people should actually be aware of, or it can be a threat that is not real but that you treat as real (whether it be a fictional/legendary threat or something that is perhaps a small threat but that you present as a big one). Your job is to convince your audience to take this threat seriously, and to do that, you will need to make use of emotional appeal (especially to fear—think back to essays one and two), logical appeal (partly use of details/facts/ evidence we discussed in essay four, but also through definition such as we worked on in essay three), and ethical appeal (your own credibility—think back to issues besides logic and evidence covered in essay four). You may choose to include outside sources if you wish, but you must cite them if you use them and indicate when you are using the words of the original source. We will discuss how to find and to cite them to prepare you to use them correctly. If writing about a fictional threat, you may wish to make up sources. If you do so, I leave it up to you whether you formally cite them (though you must do this if you are using real sources) or informally refer to them in a manner similar to what we saw in the articles we read for essay four. Turning in an essay in which significant portions are not written by you and/or without outside sources cited will result in an essay grade of zero (and not revisable for a higher grade). If you are unsure what to cite, let me know. For ideas, you may want to browse the website snopes.com. This site contains lists and research about many feasible topics for this essay. Try not to use Snopes itself as a source—most entries there contain a list of sources that would be more appropriate for you to utilize and credit in your research. You may also choose to write about a topic covered by one of the essay four articles—if you liked an issue but felt that the warning about it was not very credible, you can use this paper as an opportunity to write about that topic but in a believable, convincing way. Whatever you choose as your topic, by the end of it, you want your reader to believe that what you discuss is a real threat to them. Essay Five: Argument Paper/Warning Assignment Description English 101, Sections 26 & 30 Fall 2015 Skills We Will Cover In This Unit: • finding & citing sources • utilizing emotional, logical, and ethical appeal SCHEDULE GRADING Incomplete papers or papers that stray from the assigned topic/purpose will receive a D or F. C B A To earn at least a C, the paper should: • have a clearly established threat that it attempts to warn the reader about • cite any information obtained from outside sources • be written in such a way as it can be easily understood by the reader To earn a B, the paper should fulfill the criteria above, plus: • include at least one section intended to appeal to the reader’s emotions (especially fear) • include logical support in the form of evidence, details, or other forms of establishing logical reasoning • be organized well, which includes having a clear sense of structure and transitioning into new ideas • include only the information and discussion necessary to accomplish the purpose of the assignment • have only a few grammatical errors, and those should not interfere with understanding To earn an A, the paper should fulfill the criteria for a B paper, plus: • possess strong unity of ideas • skillfully utilize all three rhetorical appeals • make a convincing case that the threat is real • be nearly free of grammatical or wording problems FRI OCT 30 MON NOV 2 discuss “We Are Training Our Kids to Kill” (p. 481) WED NOV 4 discuss “How Bingeing Became the New College Sport” (p. 476) FRI NOV 6 Homecoming—no classes after noon, no Blackboard assignment MON NOV 9 Discuss “The Real Skinny” (p. 492) No class—Blackboard assignment: online scavenger hunt (opens Monday, due by 11:59pm on Sunday 11/1) WED NOV 11 FRI NOV 13 No class—Blackboard assignment: essay five peer review. Post your draft by noon Friday, respond to two classmates’ by 11:59pm on Monday 11/16. You may wish to review skills from previous assignments as you work on this essay: • essay one: telling a story, creating an emotional response • essay two: how to create emotional response, utilizing evidence • essay three: defining important terms, using logic • essay four: establishing character and credibility WED OCT 28 Discuss “Our Unhealthy Obsession with Sickness (p. 469) MON OCT 26 Essay Four Due; Essay Five Assigned; meet in 70-122 MON NOV 16 No class—Dr. Hill at BTW Symposium (you can attend, too!) Meet in 70-122 for research time and citing instruction MON NOV 18 Essay five due; final portfolio assigned

Objective: Persuade readers that they should fear a threat of your choosing, real or fabricated. Due Date: Wednesday, November 18th Length: 4-5 pages Format: typed, double-spaced, standard font and margins For this essay, you will be putting together all the aspects of argument that we have been learning about over the last few weeks. You will be using those elements to convince your readers that some issue of your choosing is a threat to them. This issue can be a real threat that you believe people should actually be aware of, or it can be a threat that is not real but that you treat as real (whether it be a fictional/legendary threat or something that is perhaps a small threat but that you present as a big one). Your job is to convince your audience to take this threat seriously, and to do that, you will need to make use of emotional appeal (especially to fear—think back to essays one and two), logical appeal (partly use of details/facts/ evidence we discussed in essay four, but also through definition such as we worked on in essay three), and ethical appeal (your own credibility—think back to issues besides logic and evidence covered in essay four). You may choose to include outside sources if you wish, but you must cite them if you use them and indicate when you are using the words of the original source. We will discuss how to find and to cite them to prepare you to use them correctly. If writing about a fictional threat, you may wish to make up sources. If you do so, I leave it up to you whether you formally cite them (though you must do this if you are using real sources) or informally refer to them in a manner similar to what we saw in the articles we read for essay four. Turning in an essay in which significant portions are not written by you and/or without outside sources cited will result in an essay grade of zero (and not revisable for a higher grade). If you are unsure what to cite, let me know. For ideas, you may want to browse the website snopes.com. This site contains lists and research about many feasible topics for this essay. Try not to use Snopes itself as a source—most entries there contain a list of sources that would be more appropriate for you to utilize and credit in your research. You may also choose to write about a topic covered by one of the essay four articles—if you liked an issue but felt that the warning about it was not very credible, you can use this paper as an opportunity to write about that topic but in a believable, convincing way. Whatever you choose as your topic, by the end of it, you want your reader to believe that what you discuss is a real threat to them. Essay Five: Argument Paper/Warning Assignment Description English 101, Sections 26 & 30 Fall 2015 Skills We Will Cover In This Unit: • finding & citing sources • utilizing emotional, logical, and ethical appeal SCHEDULE GRADING Incomplete papers or papers that stray from the assigned topic/purpose will receive a D or F. C B A To earn at least a C, the paper should: • have a clearly established threat that it attempts to warn the reader about • cite any information obtained from outside sources • be written in such a way as it can be easily understood by the reader To earn a B, the paper should fulfill the criteria above, plus: • include at least one section intended to appeal to the reader’s emotions (especially fear) • include logical support in the form of evidence, details, or other forms of establishing logical reasoning • be organized well, which includes having a clear sense of structure and transitioning into new ideas • include only the information and discussion necessary to accomplish the purpose of the assignment • have only a few grammatical errors, and those should not interfere with understanding To earn an A, the paper should fulfill the criteria for a B paper, plus: • possess strong unity of ideas • skillfully utilize all three rhetorical appeals • make a convincing case that the threat is real • be nearly free of grammatical or wording problems FRI OCT 30 MON NOV 2 discuss “We Are Training Our Kids to Kill” (p. 481) WED NOV 4 discuss “How Bingeing Became the New College Sport” (p. 476) FRI NOV 6 Homecoming—no classes after noon, no Blackboard assignment MON NOV 9 Discuss “The Real Skinny” (p. 492) No class—Blackboard assignment: online scavenger hunt (opens Monday, due by 11:59pm on Sunday 11/1) WED NOV 11 FRI NOV 13 No class—Blackboard assignment: essay five peer review. Post your draft by noon Friday, respond to two classmates’ by 11:59pm on Monday 11/16. You may wish to review skills from previous assignments as you work on this essay: • essay one: telling a story, creating an emotional response • essay two: how to create emotional response, utilizing evidence • essay three: defining important terms, using logic • essay four: establishing character and credibility WED OCT 28 Discuss “Our Unhealthy Obsession with Sickness (p. 469) MON OCT 26 Essay Four Due; Essay Five Assigned; meet in 70-122 MON NOV 16 No class—Dr. Hill at BTW Symposium (you can attend, too!) Meet in 70-122 for research time and citing instruction MON NOV 18 Essay five due; final portfolio assigned

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The treaty states: “That there shall be …. perpetual Oblivion, Amnesty, or Pardon of all that has been committed since the beginning of these Troubles.” Why is this important? A. It is meant to create an image of the future peace between states. B. The line in the treaty suggests that all states should mesh together forever. C. It attempts to erase the sins of the past for the sake of the future peace. D. It reaffirms the importance of religion to each state. E. This is a flourishing line that hides the truth which is that we should keep old animosities alive. The treaty says “each Party shall endeavour to procure the Benefit, Honour and Advantage of the other…” The use of the word “advantage” likely means: A. Each country needs to develop their own military to gain power. B. In this case advantage means simply to move forward from history. C. Benefit, Honour, and Advantage all mean the same thing here whichis Glory. D. Advantage is a reference to sport. E. Advantage likely means the growth of peace and economic abundance. Why is it important that states do not encourage the enemies of other countries toward hostilities? A. It would be a slippery slope to war once hostilities began. B. You would effectively be sponsoring war indirectly. C. It would upset the fundamental nature of the peace among states by fostering hostilities. D. It would be a slippery slope to war once hostilities began AND it would upset the fundamental nature of the peace among states by fostering hostilities. E. All of these options. The power structure between states in the Treaty could best be described as: A. A hierarchical system of states in which Swedeland is the ultimate ruler. B. A system of states all subsumed underneath a central emperor. C. A loose network of disconnected states who live in isolation of one another. D. A system of states living roughly in equality to one another with no overarching ruler. E. A collection of states all operating as democracies.

The treaty states: “That there shall be …. perpetual Oblivion, Amnesty, or Pardon of all that has been committed since the beginning of these Troubles.” Why is this important? A. It is meant to create an image of the future peace between states. B. The line in the treaty suggests that all states should mesh together forever. C. It attempts to erase the sins of the past for the sake of the future peace. D. It reaffirms the importance of religion to each state. E. This is a flourishing line that hides the truth which is that we should keep old animosities alive. The treaty says “each Party shall endeavour to procure the Benefit, Honour and Advantage of the other…” The use of the word “advantage” likely means: A. Each country needs to develop their own military to gain power. B. In this case advantage means simply to move forward from history. C. Benefit, Honour, and Advantage all mean the same thing here whichis Glory. D. Advantage is a reference to sport. E. Advantage likely means the growth of peace and economic abundance. Why is it important that states do not encourage the enemies of other countries toward hostilities? A. It would be a slippery slope to war once hostilities began. B. You would effectively be sponsoring war indirectly. C. It would upset the fundamental nature of the peace among states by fostering hostilities. D. It would be a slippery slope to war once hostilities began AND it would upset the fundamental nature of the peace among states by fostering hostilities. E. All of these options. The power structure between states in the Treaty could best be described as: A. A hierarchical system of states in which Swedeland is the ultimate ruler. B. A system of states all subsumed underneath a central emperor. C. A loose network of disconnected states who live in isolation of one another. D. A system of states living roughly in equality to one another with no overarching ruler. E. A collection of states all operating as democracies.

The treaty states: “That there shall be .... perpetual Oblivion, … Read More...
1 IN2009: Language Processors Coursework Part 3: The Interpreter Introduction This is the 3rd and final part of the coursework. In the second part of the coursework you created a parser for the Moopl grammar which, given a syntactically correct Moopl program as input, builds an AST representation of the program. In Part 3 you will develop an interpreter which executes Moopl programs by visiting their AST representations. For this part of the coursework we provide functional code (with limitations, see below) for parsing, building a symbol table, type checking and variable allocation. Marks This part of the coursework is worth 12 of the 30 coursework marks for the Language Processors module. This part of the coursework is marked out of 12. Submission deadline This part of the coursework should be handed in before 5pm on Sunday 9th April 2017. In line with school policy, late submissions will be awarded no marks. Return & Feedback Marks and feedback will be available as soon as possible, certainly on or before Wed 3rd May 2017. Plagiarism If you copy the work of others (either that of fellow students or of a third party), with or without their permission, you will score no marks and further disciplinary action will be taken against you. Group working You will be working in the same groups as for the previous parts of the coursework except where group changes have already been approved. Submission: Submit a zip archive (not a rar file) of all your source code (the src folder of your project). We do not want the other parts of your NetBeans project, only the source code. Note 1: Submissions which do not compile will get zero marks. Note 2: You must not change the names or types of any of the existing packages, classes or public methods. 2 Getting started Download either moopl-interp.zip or moopl-interp.tgz from Moodle and extract all files. Key contents to be aware of: • A fully implemented Moopl parser (also implements a parser for the interpreter command language; see below). • A partially implemented Moopl type checker. • Test harnesses for the type checker and interpreter. • A directory of a few example Moopl programs (see Testing below). • Folder interp containing prototype interpreter code. The type-checker is only partially implemented but a more complete implementation will be provided following Session 6. That version is still not fully complete because it doesn’t support inheritance. Part d) below asks you to remove this restriction. The VarAllocator visitor in the interp package uses a simple implementation which only works for methods in which all parameter and local variable names are different. Part e) below asks you to remove this restriction. The three parts below should be attempted in sequence. When you have completed one part you should make a back-up copy of the work and keep it safe, in case you break it in your attempt at the next part. Be sure to test old functionality as well as new (regression testing). We will not assess multiple versions so, if your attempt at part d) or e) breaks previously working code, you may gain a better mark by submitting the earlier version for assessment. c) [8 marks] The Basic Interpreter: complete the implementation of the Interpreter visitor in the interp package. d) [2 marks] Inheritance: extend the type-checker, variable allocator and interpreter to support inheritance. e) [2 marks] Variable Allocation: extend the variable allocator to fully support blockstructure and lexical scoping, removing the requirement that all parameter and local variable names are different. Aim to minimise the number of local variable slots allocated in a stack frame. Note: variable and parameter names declared at the same scope level are still required to be different from each other (a method cannot have two different parameters called x, for example) and this is enforced by the existing typechecking code. But variables declared in different blocks (even when nested) can have the same name. Exceptions Your interpreter will only ever be run on Moopl code which is type-correct (and free from uninitialised local variables). But it is still possible that the Moopl code contains logical errors which may cause runtime errors (such as null-reference or array-bound errors). Your interpreter should throw a MooplRunTimeException with an appropriate error message in these cases. The only kind of exception your interpreter should ever throw is a MooplRunTimeException. 3 Testing The examples folder does not contain a comprehensive test-suite. You need to invent and run your own tests. The document Moopl compared with Java gives a concise summary of how Moopl programs are supposed to behave. You can (and should) also compare the behaviour of your interpreter with that of the online tool: https://smcse.city.ac.uk/student/sj353/langproc/Moopl.html (Note: the online tool checks for uninitialised local variables. Your implementation is not expected to do this.) To test your work, run the top-level Interpret harness, providing the name of a Moopl source file as a command-line argument. When run on a type-correct Moopl source file, Interpret will pretty-print the Moopl program then display a command prompt (>) at which you can enter one of the following commands: :quit This will quit the interpreter. :call main() This will call the top-level proc main, interpreted in the context defined by the Moopl program. (Any top-level proc can be called this way). :eval Exp ; This will evaluate expression Exp, interpreted in the context defined by the Moopl program, and print the result. Note the required terminating semi-colon. Testing your Expression visitors To unit-test your Exp visit methods, run the top-level Interpret harness on a complete Moopl program (though it can be trivial) and use the :eval command. For example, to test your visit methods for the Boolean-literals (ExpTrue and ExpFalse), you would enter the commands > :eval true ; > :eval false ; which should output 1 and 0, respectively. For the most basic cases, the Moopl program is essentially irrelevant (a single top-level proc with empty body may be sufficient). For other cases you will need to write programs containing class definitions (in order, for example, to test object creation and method call). Testing your Statement visitors To unit-test your Stm visit methods, write very simple Moopl programs, each with a top-level proc main() containing just a few lines of code. Run the top-level Interpret harness on these simple programs and enter the command > :call main() You will find a few examples to get you started in the folder examples/unittests. As for the Exp tests, simple cases can be tested using Moopl programs with just a main proc but for the more complex tests you will need to write Moopl programs containing class definitions. 4 Grading criteria Solutions will be graded according to their functional correctness, and the elegance of their implementation. Below are criteria that guide the award of marks. 70 – 100 [1st class] Work that meets all the requirements in full, constructed and presented to a professional standard. Showing evidence of independent reading, thinking and analysis. 60 – 69 [2:1] Work that makes a good attempt to address the requirements, realising all to some extent and most well. Well-structured and well presented. 50 – 59 [2:2] Work that attempts to address requirements realising all to some extent and some well but perhaps also including irrelevant or underdeveloped material. Structure and presentation may not always be clear. 40 – 49 [3rd class] Work that attempts to address the requirements but only realises them to some extent and may not include important elements or be completely accurate. Structure and presentation may lack clarity. 0 – 39 [fail] Unsatisfactory work that does not adequately address the requirements. Structure and presentation may be confused or incoherent.

1 IN2009: Language Processors Coursework Part 3: The Interpreter Introduction This is the 3rd and final part of the coursework. In the second part of the coursework you created a parser for the Moopl grammar which, given a syntactically correct Moopl program as input, builds an AST representation of the program. In Part 3 you will develop an interpreter which executes Moopl programs by visiting their AST representations. For this part of the coursework we provide functional code (with limitations, see below) for parsing, building a symbol table, type checking and variable allocation. Marks This part of the coursework is worth 12 of the 30 coursework marks for the Language Processors module. This part of the coursework is marked out of 12. Submission deadline This part of the coursework should be handed in before 5pm on Sunday 9th April 2017. In line with school policy, late submissions will be awarded no marks. Return & Feedback Marks and feedback will be available as soon as possible, certainly on or before Wed 3rd May 2017. Plagiarism If you copy the work of others (either that of fellow students or of a third party), with or without their permission, you will score no marks and further disciplinary action will be taken against you. Group working You will be working in the same groups as for the previous parts of the coursework except where group changes have already been approved. Submission: Submit a zip archive (not a rar file) of all your source code (the src folder of your project). We do not want the other parts of your NetBeans project, only the source code. Note 1: Submissions which do not compile will get zero marks. Note 2: You must not change the names or types of any of the existing packages, classes or public methods. 2 Getting started Download either moopl-interp.zip or moopl-interp.tgz from Moodle and extract all files. Key contents to be aware of: • A fully implemented Moopl parser (also implements a parser for the interpreter command language; see below). • A partially implemented Moopl type checker. • Test harnesses for the type checker and interpreter. • A directory of a few example Moopl programs (see Testing below). • Folder interp containing prototype interpreter code. The type-checker is only partially implemented but a more complete implementation will be provided following Session 6. That version is still not fully complete because it doesn’t support inheritance. Part d) below asks you to remove this restriction. The VarAllocator visitor in the interp package uses a simple implementation which only works for methods in which all parameter and local variable names are different. Part e) below asks you to remove this restriction. The three parts below should be attempted in sequence. When you have completed one part you should make a back-up copy of the work and keep it safe, in case you break it in your attempt at the next part. Be sure to test old functionality as well as new (regression testing). We will not assess multiple versions so, if your attempt at part d) or e) breaks previously working code, you may gain a better mark by submitting the earlier version for assessment. c) [8 marks] The Basic Interpreter: complete the implementation of the Interpreter visitor in the interp package. d) [2 marks] Inheritance: extend the type-checker, variable allocator and interpreter to support inheritance. e) [2 marks] Variable Allocation: extend the variable allocator to fully support blockstructure and lexical scoping, removing the requirement that all parameter and local variable names are different. Aim to minimise the number of local variable slots allocated in a stack frame. Note: variable and parameter names declared at the same scope level are still required to be different from each other (a method cannot have two different parameters called x, for example) and this is enforced by the existing typechecking code. But variables declared in different blocks (even when nested) can have the same name. Exceptions Your interpreter will only ever be run on Moopl code which is type-correct (and free from uninitialised local variables). But it is still possible that the Moopl code contains logical errors which may cause runtime errors (such as null-reference or array-bound errors). Your interpreter should throw a MooplRunTimeException with an appropriate error message in these cases. The only kind of exception your interpreter should ever throw is a MooplRunTimeException. 3 Testing The examples folder does not contain a comprehensive test-suite. You need to invent and run your own tests. The document Moopl compared with Java gives a concise summary of how Moopl programs are supposed to behave. You can (and should) also compare the behaviour of your interpreter with that of the online tool: https://smcse.city.ac.uk/student/sj353/langproc/Moopl.html (Note: the online tool checks for uninitialised local variables. Your implementation is not expected to do this.) To test your work, run the top-level Interpret harness, providing the name of a Moopl source file as a command-line argument. When run on a type-correct Moopl source file, Interpret will pretty-print the Moopl program then display a command prompt (>) at which you can enter one of the following commands: :quit This will quit the interpreter. :call main() This will call the top-level proc main, interpreted in the context defined by the Moopl program. (Any top-level proc can be called this way). :eval Exp ; This will evaluate expression Exp, interpreted in the context defined by the Moopl program, and print the result. Note the required terminating semi-colon. Testing your Expression visitors To unit-test your Exp visit methods, run the top-level Interpret harness on a complete Moopl program (though it can be trivial) and use the :eval command. For example, to test your visit methods for the Boolean-literals (ExpTrue and ExpFalse), you would enter the commands > :eval true ; > :eval false ; which should output 1 and 0, respectively. For the most basic cases, the Moopl program is essentially irrelevant (a single top-level proc with empty body may be sufficient). For other cases you will need to write programs containing class definitions (in order, for example, to test object creation and method call). Testing your Statement visitors To unit-test your Stm visit methods, write very simple Moopl programs, each with a top-level proc main() containing just a few lines of code. Run the top-level Interpret harness on these simple programs and enter the command > :call main() You will find a few examples to get you started in the folder examples/unittests. As for the Exp tests, simple cases can be tested using Moopl programs with just a main proc but for the more complex tests you will need to write Moopl programs containing class definitions. 4 Grading criteria Solutions will be graded according to their functional correctness, and the elegance of their implementation. Below are criteria that guide the award of marks. 70 – 100 [1st class] Work that meets all the requirements in full, constructed and presented to a professional standard. Showing evidence of independent reading, thinking and analysis. 60 – 69 [2:1] Work that makes a good attempt to address the requirements, realising all to some extent and most well. Well-structured and well presented. 50 – 59 [2:2] Work that attempts to address requirements realising all to some extent and some well but perhaps also including irrelevant or underdeveloped material. Structure and presentation may not always be clear. 40 – 49 [3rd class] Work that attempts to address the requirements but only realises them to some extent and may not include important elements or be completely accurate. Structure and presentation may lack clarity. 0 – 39 [fail] Unsatisfactory work that does not adequately address the requirements. Structure and presentation may be confused or incoherent.

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