This week serves an opportunity for you to serve as a public relations strategist! Go to any respectable media outlet (online, tv, print, etc). Find a story that provides an example of a public relations problem or opportunity. It can be local, state, regional, national or international in nature. (Note: no fair citing the obvious; try to be creative in your story choice). 1) list the story link so we can refer to it when we are responding in the forum 2) provide a brief recap of the situation. (This should serve as about 1/2 of your posting) 3) provide a brief recommendation/suggestion of how the company/organization/celebrity, etc. should handle it from a public relations perspective. REMEMBER: it doesn’t have to be negative! (This should serve as the other 1/2 of your posting) 4) provide a question for your colleagues to ponder/respond to in the forum.

This week serves an opportunity for you to serve as a public relations strategist! Go to any respectable media outlet (online, tv, print, etc). Find a story that provides an example of a public relations problem or opportunity. It can be local, state, regional, national or international in nature. (Note: no fair citing the obvious; try to be creative in your story choice). 1) list the story link so we can refer to it when we are responding in the forum 2) provide a brief recap of the situation. (This should serve as about 1/2 of your posting) 3) provide a brief recommendation/suggestion of how the company/organization/celebrity, etc. should handle it from a public relations perspective. REMEMBER: it doesn’t have to be negative! (This should serve as the other 1/2 of your posting) 4) provide a question for your colleagues to ponder/respond to in the forum.

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ENG 100 – Critique Assignment Sheet Rough Draft Due for Peer Response: Tuesday, September 29 First Draft Due (submit for feedback): Thursday, October 1 Final Draft with Outline Due: Thursday, October 8 Highlighting, Labeling, and Reflection: Thursday, October 8 Submit hard copies in class and upload to turnitin.com (Password: English, Class ID: 10423941) What is a Critique? A critique is a “formal evaluation [that offers your] judgment of a text—whether the reading was effective, ineffective, valuable, or trivial.” In a critique, “your goal is to convince readers to accept your judgments concerning the quality of the reading” based on specific criteria you have established (Wilhoit 87). Additionally, a critique is comprised of many integrated parts: introduction to the text, introduction to and brief background on the general topic, brief summary properly placed in the essay, a discussion of the criteria chosen for evaluation, a discussion of the criteria using specific examples/information from the text (this discussion should be the largest section of your essay by far!!), instances of personal response, and a conclusion. All of these items should relate to your overall evaluation/thesis of the text. The Assignment: Instead of a written essay, your “text” will be either a movie or a documentary. You will follow the same standards that you would use for a critique based off of an essay but you will adapt the integrated parts to fit a film critique. In order to effectively address this assignment, complete the following steps: STEP I: Choose either a movie or documentary • Base your choice on the strength of your feelings, whether hate, love, respect, etc., because you do not have to like the film in order to write a solid and coherent critique. You might have more to say about a film you dislike. Also choose a genre of film that you understand (i.e. romantic comedy, drama, indie-film, comedy, documentary). • Think about the important components for this specific genre. STEP II: Watch and Annotate the film • Note the major points within the film, how you felt while watching it, and what made you feel that way. • Keep in mind the film’s genre and whether or not your chosen film fits any of those criteria. STEP III: Analyze (break the film into parts) • Break the film down into your genre-driven criteria. • Choose 4-5 criteria and then determine what sections/components of the film either represent effectiveness or ineffectiveness. STEP IV: Evaluate the film (using the criteria and your personal standards) • Evaluate the film according to the criteria list we will generate in class. • To help create your thesis claim, determine whether the film, based on your criteria and standards, is an excellent, mediocre, terrible, etc. representation of your chosen genre. • For example: While the costume and design are fantastic and interesting, the film 300 is a mediocre example of historical drama because the history of Greece and Asia is inaccurate and the female characters are weak. STEP V: Find outside sources—one should agree with you and one should disagree • Check out a review website, such as imdb.com, and locate a few reviews of your film. In your critique, you will be expected to reference other film reviewers to develop and support your own arguments. Please note that those reviews must be cited properly, both in-text citations and the Works Cited page entries. The basic structure of the critique is as follows: • An introduction that o Introduces the film and provides an adequate amount of background information, including the intended audience, to give the reader context (i.e. a cartoon might not be meant for college-age viewers) o Includes a thesis statement that presents the film as either an excellent, mediocre, or terrible representation of your chosen genre o Explains at least three-four different criteria as the basis for your thesis/argument • A summary that is o Brief, neutral and comprehensive o No more than one paragraph in length • Body Paragraphs including o Support of your thesis using specific examples from the film o More than one example to support your argument o Either direct quotes or paraphrased information from the source text, reviews, outside information (websites, blogs, credible sources) or a combination of all three to support your argument • A counter-claim o Based on an outside review/blog/article disagreeing with your opinion or one criteria o Includes either a refutation or concession of the reviewer’s opinion • A conclusion including o A restatement of your main points and thesis o A final recommendation • A Work Cited page that o Includes all referenced materials including the source text The bulk of your critique should consist of your qualified opinion of the film – unlike the summary, your opinion matters here. In the body of your paper, you will need about three to five main points to support your thesis statement. You will develop each of these points in a section of your essay, each section consisting of about three paragraphs. You will make claims in your topic sentences, provide examples from the text, and then explain your reasons, using source support where possible. Evaluation A successful critique will contain all of the following: • Creative and clearly stated criteria • A debatable thesis statement • A brief background and summary of the film • 80% of the essay is located within the body paragraphs • Topic sentences that transition from one criteria to the next • Body paragraphs clearly and accurately reflecting your criteria and opinion • Body paragraphs that include more than one example as support • Conclusion including a summation and thoughtful recommendation • Correct MLA documentation including signal phrases and in-text citations • A Work Cited page including all sources referenced • Correct grammar and mechanics • Effective and meaningful transitions • Meaningful and descriptive word choices • Literary present tense and grammatical 3rd person • Length of 3-5 pages • Follows the basic structure for a critique Possible Points (25 % of final grade): • Outline 5 % • Peer Response Workshop with Rough Draft 5 % • Highlighted Revisions, & Reflection 10 % • Final Draft: 80 % Upload to Turnitin.com, using Password: English and Class ID: 10423941. Your grade will not be finalized until you have done this.

ENG 100 – Critique Assignment Sheet Rough Draft Due for Peer Response: Tuesday, September 29 First Draft Due (submit for feedback): Thursday, October 1 Final Draft with Outline Due: Thursday, October 8 Highlighting, Labeling, and Reflection: Thursday, October 8 Submit hard copies in class and upload to turnitin.com (Password: English, Class ID: 10423941) What is a Critique? A critique is a “formal evaluation [that offers your] judgment of a text—whether the reading was effective, ineffective, valuable, or trivial.” In a critique, “your goal is to convince readers to accept your judgments concerning the quality of the reading” based on specific criteria you have established (Wilhoit 87). Additionally, a critique is comprised of many integrated parts: introduction to the text, introduction to and brief background on the general topic, brief summary properly placed in the essay, a discussion of the criteria chosen for evaluation, a discussion of the criteria using specific examples/information from the text (this discussion should be the largest section of your essay by far!!), instances of personal response, and a conclusion. All of these items should relate to your overall evaluation/thesis of the text. The Assignment: Instead of a written essay, your “text” will be either a movie or a documentary. You will follow the same standards that you would use for a critique based off of an essay but you will adapt the integrated parts to fit a film critique. In order to effectively address this assignment, complete the following steps: STEP I: Choose either a movie or documentary • Base your choice on the strength of your feelings, whether hate, love, respect, etc., because you do not have to like the film in order to write a solid and coherent critique. You might have more to say about a film you dislike. Also choose a genre of film that you understand (i.e. romantic comedy, drama, indie-film, comedy, documentary). • Think about the important components for this specific genre. STEP II: Watch and Annotate the film • Note the major points within the film, how you felt while watching it, and what made you feel that way. • Keep in mind the film’s genre and whether or not your chosen film fits any of those criteria. STEP III: Analyze (break the film into parts) • Break the film down into your genre-driven criteria. • Choose 4-5 criteria and then determine what sections/components of the film either represent effectiveness or ineffectiveness. STEP IV: Evaluate the film (using the criteria and your personal standards) • Evaluate the film according to the criteria list we will generate in class. • To help create your thesis claim, determine whether the film, based on your criteria and standards, is an excellent, mediocre, terrible, etc. representation of your chosen genre. • For example: While the costume and design are fantastic and interesting, the film 300 is a mediocre example of historical drama because the history of Greece and Asia is inaccurate and the female characters are weak. STEP V: Find outside sources—one should agree with you and one should disagree • Check out a review website, such as imdb.com, and locate a few reviews of your film. In your critique, you will be expected to reference other film reviewers to develop and support your own arguments. Please note that those reviews must be cited properly, both in-text citations and the Works Cited page entries. The basic structure of the critique is as follows: • An introduction that o Introduces the film and provides an adequate amount of background information, including the intended audience, to give the reader context (i.e. a cartoon might not be meant for college-age viewers) o Includes a thesis statement that presents the film as either an excellent, mediocre, or terrible representation of your chosen genre o Explains at least three-four different criteria as the basis for your thesis/argument • A summary that is o Brief, neutral and comprehensive o No more than one paragraph in length • Body Paragraphs including o Support of your thesis using specific examples from the film o More than one example to support your argument o Either direct quotes or paraphrased information from the source text, reviews, outside information (websites, blogs, credible sources) or a combination of all three to support your argument • A counter-claim o Based on an outside review/blog/article disagreeing with your opinion or one criteria o Includes either a refutation or concession of the reviewer’s opinion • A conclusion including o A restatement of your main points and thesis o A final recommendation • A Work Cited page that o Includes all referenced materials including the source text The bulk of your critique should consist of your qualified opinion of the film – unlike the summary, your opinion matters here. In the body of your paper, you will need about three to five main points to support your thesis statement. You will develop each of these points in a section of your essay, each section consisting of about three paragraphs. You will make claims in your topic sentences, provide examples from the text, and then explain your reasons, using source support where possible. Evaluation A successful critique will contain all of the following: • Creative and clearly stated criteria • A debatable thesis statement • A brief background and summary of the film • 80% of the essay is located within the body paragraphs • Topic sentences that transition from one criteria to the next • Body paragraphs clearly and accurately reflecting your criteria and opinion • Body paragraphs that include more than one example as support • Conclusion including a summation and thoughtful recommendation • Correct MLA documentation including signal phrases and in-text citations • A Work Cited page including all sources referenced • Correct grammar and mechanics • Effective and meaningful transitions • Meaningful and descriptive word choices • Literary present tense and grammatical 3rd person • Length of 3-5 pages • Follows the basic structure for a critique Possible Points (25 % of final grade): • Outline 5 % • Peer Response Workshop with Rough Draft 5 % • Highlighted Revisions, & Reflection 10 % • Final Draft: 80 % Upload to Turnitin.com, using Password: English and Class ID: 10423941. Your grade will not be finalized until you have done this.

info@checkyourstudy.com
Lectorial 5: The Gravitron The Gravitron (shown in figure 1 [1]) is a carnival ride designed to simulate the experience of zero gravity. The ride consists of a 15 metre diameter circular chamber which spins around a centre shaft. The spinning motion applies a force to the occupants of the ride pinning them up against their seat. Figure 1: The Gravitron carnival ride. For this lectorial task we want to study the forces being applied to the ride’s occupants and determine the g-forces they would be experiencing. According to physics, the rules for uniform circular motion are: where: 1. If the ride has a maximum rotational speed of 24 revolutions per minute (rpm), determine the force being applied to the ride’s occupants. What gforces are the people experiencing (assume occupants are 65 kg adults)? [1] “Gravitron” used under Creative Commons licence (https://creativecommons.org/licenses/by-nc-sa/2.0/). Photo by: bobdole369 Newtons 2 r v F = ma = m angular speed in radians per second rotational speed in revolutions per second (or Hz) radius of the Gravitron tangential velocity of the Gravitron mass of occupant = = = = = w f r v m -1 v = wr ms w = 2pf rad/sec Typically the Gravitron ride takes approximately 20 seconds to reach its maximum rotational speed of 24 rpms and the whole ride lasts for around 80 seconds. This means the ride’s occupants are exposed to non-uniform circular motion meaning there is changing linear velocity at certain parts of the ride. For non-uniform circular motion the following formulae are useful: where: A GPS tracking device was attached to a person in the Gravitron and data was obtained about their x,y displacement vs. time over the 80 second duration of the ride. The data was saved in a .csv file called ‘gravitron.csv.’ This file contains three columns: time, x-displacement and y-displacement, e.g.: Time, sec x-displacement y-displacement 0.00 0.10 0.20 … 2. Download this .csv file from Blackboard. Find the g-forces being applied to the ride’s occupants for the whole 80 second duration of the ride. Again assume the occupants are 65 kg adults. Think about how you could effectively present these results. -2 2 ms r v -1 a = 2 2 ms     +     = dt dy dt dx v centripetal acceleration time in seconds displacement in y direction displacement in x direction = = = = a t y x

Lectorial 5: The Gravitron The Gravitron (shown in figure 1 [1]) is a carnival ride designed to simulate the experience of zero gravity. The ride consists of a 15 metre diameter circular chamber which spins around a centre shaft. The spinning motion applies a force to the occupants of the ride pinning them up against their seat. Figure 1: The Gravitron carnival ride. For this lectorial task we want to study the forces being applied to the ride’s occupants and determine the g-forces they would be experiencing. According to physics, the rules for uniform circular motion are: where: 1. If the ride has a maximum rotational speed of 24 revolutions per minute (rpm), determine the force being applied to the ride’s occupants. What gforces are the people experiencing (assume occupants are 65 kg adults)? [1] “Gravitron” used under Creative Commons licence (https://creativecommons.org/licenses/by-nc-sa/2.0/). Photo by: bobdole369 Newtons 2 r v F = ma = m angular speed in radians per second rotational speed in revolutions per second (or Hz) radius of the Gravitron tangential velocity of the Gravitron mass of occupant = = = = = w f r v m -1 v = wr ms w = 2pf rad/sec Typically the Gravitron ride takes approximately 20 seconds to reach its maximum rotational speed of 24 rpms and the whole ride lasts for around 80 seconds. This means the ride’s occupants are exposed to non-uniform circular motion meaning there is changing linear velocity at certain parts of the ride. For non-uniform circular motion the following formulae are useful: where: A GPS tracking device was attached to a person in the Gravitron and data was obtained about their x,y displacement vs. time over the 80 second duration of the ride. The data was saved in a .csv file called ‘gravitron.csv.’ This file contains three columns: time, x-displacement and y-displacement, e.g.: Time, sec x-displacement y-displacement 0.00 0.10 0.20 … 2. Download this .csv file from Blackboard. Find the g-forces being applied to the ride’s occupants for the whole 80 second duration of the ride. Again assume the occupants are 65 kg adults. Think about how you could effectively present these results. -2 2 ms r v -1 a = 2 2 ms     +     = dt dy dt dx v centripetal acceleration time in seconds displacement in y direction displacement in x direction = = = = a t y x

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Essay list

Essay list

      Some students have a background or story … Read More...
Explain the significant impact this career development experience has had and will continue to have on your life.

Explain the significant impact this career development experience has had and will continue to have on your life.

Most corporate individuals instinctively comprehend the connection between well-designed creativities … Read More...
5. Provide a brief discussion with supporting evidence to the following inquiry: With the responsibility of overseeing career development processes, how does management equip employees with skills that impact their performance in an efficient and effective manner?

5. Provide a brief discussion with supporting evidence to the following inquiry: With the responsibility of overseeing career development processes, how does management equip employees with skills that impact their performance in an efficient and effective manner?

Career development can facilitate we attain superior contentment and accomplishment. … Read More...
1-Two notions serve as the basis for all torts: wrongs and compensation. True False 2-The goal of tort law is to put a defendant in the position that he or she would have been in had the tort occurred to the defendant. True False 3-Hayley is injured in an accident precipitated by Isolde. Hayley files a tort action against Isolde, seeking to recover for the damage suffered. Damages that are intended to compensate or reimburse a plaintiff for actual losses are: compensatory damages. reimbursement damages. actual damages. punitive damages. 4-Ladd throws a rock intending to hit Minh but misses and hits Nasir instead. On the basis of the tort of battery, Nasir can sue: Ladd. Minh. the rightful owner of the rock. no one. 4-Luella trespasses on Merchandise Mart’s property. Through the use of reasonable force, Merchandise Mart’s security guard detains Luella until the police arrive. Merchandise Mart is liable for: assault. battery. false imprisonment. none of the choice 6-The extreme risk of an activity is a defense against imposing strict liability. True False 7-Misrepresentation in an ad is enough to show an intent to induce the reliance of anyone who may use the product. True False 8-Luke is playing a video game on a defective disk that melts in his game player, starting a fire that injures his hands. Luke files a suit against Mystic Maze, Inc., the game’s maker under the doctrine of strict liability. A significant application of this doctrine is in the area of: cyber torts. intentional torts. product liability. unintentional torts 9-More than two hundred years ago, the Declaration of Independence recognized the importance of protecting creative works. True False 10-n 2014, Cloud Computing Corporation registers its trademark as provided by federal law. After the first renewal, this registration: is renewable every ten years. is renewable every twenty years. runs for life of the corporation plus seventy years. runs forever. 11-Wendy works as a weather announcer for a TV station under the character name Weather Wendy. Wendy can register her character’s name as: a certification mark. a trade name. a service mark. none of the choices 12-Much of the material on the Internet, including software and database information, is not copyrighted. True False 13-In a criminal case, the state must prove its case by a preponderance of the evidence. True False 14-Under the Fourth Amendmentt, general searches through a person’s belongings are permissible. True False 15-Maura enters a gas station and points a gun at the clerk Nate. She then forces Nate to open the cash register and give her all the money. Maura can be charged with: burglary. robbery. larceny. receiving stolen property. 16-Reno, driving while intoxicated, causes a car accident that results in the death of Santo. Reno is arrested and charged with a felony. A felony is a crime punishable by death or imprisonment for: any period of time. more than one year. more than six months. more than ten days. 17-Corporate officers and directors may be held criminally liable for the actions of employees under their supervision. True False 18-Sal assures Tom that she will deliver a truckload of hay to his cattle ranch. A person’s declaration to do a certain act is part of the definition of: an expectation. a moral obligation. a prediction. a promise. 19-Lark promises to buy Mac’s used textbook for $60. Lark is: an offeror. an offeree a promisee. a promisor. 20-Casey offers to sell a certain used forklift to DIY Lumber Outlet, but Casey dies before DIY accepts. Most likely, Casey’s death: did not affect the offer. shortened the time of the offer but did not terminated it. extended the time of the offer. terminated the offer.

1-Two notions serve as the basis for all torts: wrongs and compensation. True False 2-The goal of tort law is to put a defendant in the position that he or she would have been in had the tort occurred to the defendant. True False 3-Hayley is injured in an accident precipitated by Isolde. Hayley files a tort action against Isolde, seeking to recover for the damage suffered. Damages that are intended to compensate or reimburse a plaintiff for actual losses are: compensatory damages. reimbursement damages. actual damages. punitive damages. 4-Ladd throws a rock intending to hit Minh but misses and hits Nasir instead. On the basis of the tort of battery, Nasir can sue: Ladd. Minh. the rightful owner of the rock. no one. 4-Luella trespasses on Merchandise Mart’s property. Through the use of reasonable force, Merchandise Mart’s security guard detains Luella until the police arrive. Merchandise Mart is liable for: assault. battery. false imprisonment. none of the choice 6-The extreme risk of an activity is a defense against imposing strict liability. True False 7-Misrepresentation in an ad is enough to show an intent to induce the reliance of anyone who may use the product. True False 8-Luke is playing a video game on a defective disk that melts in his game player, starting a fire that injures his hands. Luke files a suit against Mystic Maze, Inc., the game’s maker under the doctrine of strict liability. A significant application of this doctrine is in the area of: cyber torts. intentional torts. product liability. unintentional torts 9-More than two hundred years ago, the Declaration of Independence recognized the importance of protecting creative works. True False 10-n 2014, Cloud Computing Corporation registers its trademark as provided by federal law. After the first renewal, this registration: is renewable every ten years. is renewable every twenty years. runs for life of the corporation plus seventy years. runs forever. 11-Wendy works as a weather announcer for a TV station under the character name Weather Wendy. Wendy can register her character’s name as: a certification mark. a trade name. a service mark. none of the choices 12-Much of the material on the Internet, including software and database information, is not copyrighted. True False 13-In a criminal case, the state must prove its case by a preponderance of the evidence. True False 14-Under the Fourth Amendmentt, general searches through a person’s belongings are permissible. True False 15-Maura enters a gas station and points a gun at the clerk Nate. She then forces Nate to open the cash register and give her all the money. Maura can be charged with: burglary. robbery. larceny. receiving stolen property. 16-Reno, driving while intoxicated, causes a car accident that results in the death of Santo. Reno is arrested and charged with a felony. A felony is a crime punishable by death or imprisonment for: any period of time. more than one year. more than six months. more than ten days. 17-Corporate officers and directors may be held criminally liable for the actions of employees under their supervision. True False 18-Sal assures Tom that she will deliver a truckload of hay to his cattle ranch. A person’s declaration to do a certain act is part of the definition of: an expectation. a moral obligation. a prediction. a promise. 19-Lark promises to buy Mac’s used textbook for $60. Lark is: an offeror. an offeree a promisee. a promisor. 20-Casey offers to sell a certain used forklift to DIY Lumber Outlet, but Casey dies before DIY accepts. Most likely, Casey’s death: did not affect the offer. shortened the time of the offer but did not terminated it. extended the time of the offer. terminated the offer.

1-Two notions serve as the basis for all torts: wrongs … Read More...
My Success Assignment ‘where you want to be in ten years’ Objective Make a plan and try to see all the details. Does some research, ask questions, and consider what it’s going to take to get where you want to be.

My Success Assignment ‘where you want to be in ten years’ Objective Make a plan and try to see all the details. Does some research, ask questions, and consider what it’s going to take to get where you want to be.

  My Road map for career planning is based on … Read More...
5 { GRAVITATION Last Updated: July 16, 2012 Problem List 5.1 Total mass of a shell 5.2 Tunnel through the moon 5.3 Gravitational eld above the center of a thin hoop 5.4 Gravitational force near a metal-cored planet surrounded by a gaseous cloud 5.5 Sphere with linearly increasing mass density 5.6 Jumping o Vesta 5.7 Gravitational force between two massive rods 5.8 Potential energy { Check your answer! 5.9 Ways of solving gravitational problems 5.10 Rod with linearly increasing mass density 5.11 Sphere with constant internal gravitational eld 5.12 Throwing a rock o the moon These problems are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Un- ported License. Please share and/or modify. Back to Problem List 1 5 { GRAVITATION Last Updated: July 16, 2012 5.1 Total mass of a shell Given: Marino { Fall 2011 Consider a spherical shell that extends from r = R to r = 2R with a non-uniform density (r) = 0r. What is the total mass of the shell? Back to Problem List 2 5 { GRAVITATION Last Updated: July 16, 2012 5.2 Tunnel through the moon Given: Marino { Fall 2011 Imagine that NASA digs a straight tunnel through the center of the moon (see gure) to access the Moon’s 3He deposits. An astronaut places a rock in the tunnel at the surface of the moon, and releases it (from rest). Show that the rock obeys the force law for a mass connected to a spring. What is the spring constant? Find the oscillation period for this motion if you assume that Moon has a mass of 7.351022 kg and a radius of 1.74106 m. Assume the moon’s density is uniform throughout its volume, and ignore the moon’s rotation. Given: Pollock { Spring 2011 Imagine (in a parallel universe of unlimited budgets) that NASA digs a straight tunnel through the center of the moon (see gure). A robot place a rock in the tunnel at position r = r0 from the center of the moon, and releases it (from rest). Use Newton’s second law to write the equation of motion of the rock and solve for r(t). Explain in words the rock’s motion. Does the rock return to its initial position at any later time? If so, how long does it takes to return to it? (Give a formula, and a number.) Assume the moon’s density is uniform throughout its volume, and ignore the moon’s rotation. Given: Pollock { Spring 2012 Now lets consider our (real) planet Earth, with total mass M and radius R which we will approximate as a uniform mass density, (r) = 0. (a) Neglecting rotational and frictional e ects, show that a particle dropped into a hole drilled straight through the center of the earth all the way to the far side will oscillate between the two endpoints. (Hint: you will need to set up, and solve, an ODE for the motion) (b) Find the period of the oscillation of this motion. Get a number (in minutes) as a nal result, using data for the earth’s size and mass. (How does that compare to ying to Perth and back?!) Extra Credit: OK, even with unlimited budgets, digging a tunnel through the center of the earth is preposterous. But, suppose instead that the tunnel is a straight-line \chord” through the earth, say directly from New York to Los Angeles. Show that your nal answer for the time taken does not depend on the location of that chord! This is rather remarkable – look again at the time for a free-fall trip (no energy required, except perhaps to compensate for friction) How long would that trip take? Could this work?! Back to Problem List 3 5 { GRAVITATION Last Updated: July 16, 2012 5.3 Gravitational eld above the center of a thin hoop Given: Pollock { Spring 2011, Spring 2012 Consider a very (in nitesimally!) thin but massive loop, radius R (total mass M), centered around the origin, sitting in the x-y plane. Assume it has a uniform linear mass density  (which has units of kg/m) all around it. (So, it’s like a skinny donut that is mostly hole, centered around the z-axis) (a) What is  in terms of M and R? What is the direction of the gravitational eld generated by this mass distribution at a point in space a distance z above the center of the donut, i.e. at (0; 0; z) Explain your reasoning for the direction carefully, try not to simply \wave your hands.” (The answer is extremely intuitive, but can you justify that it is correct?) (b) Compute the gravitational eld, ~g, at the point (0; 0; z) by directly integrating Newton’s law of gravity, summing over all in nitesimal \chunks” of mass along the loop. (c) Compute the gravitational potential at the point (0; 0; z) by directly integrating ?Gdm=r, sum- ming over all in nitesimal \chunks” dm along the loop. Then, take the z-component of the gradient of this potential to check that you agree with your result from the previous part. (d) In the two separate limits z << R and z >> R, Taylor expand your g- eld (in the z-direction)out only to the rst non-zero term, and convince us that both limits make good physical sense. (e) Can you use Gauss’ law to gure out the gravitational potential at the point (0; 0; z)? (If so, do it and check your previous answers. If not, why not?) Extra credit: If you place a small mass a small distance z away from the center, use your Taylor limit for z << R above to write a simple ODE for the equation of motion. Solve it, and discuss the motion Back to Problem List 4 5 { GRAVITATION Last Updated: July 16, 2012 5.4 Gravitational force near a metal-cored planet surrounded by a gaseous cloud Given: Pollock { Spring 2011 Jupiter is composed of a dense spherical core (of liquid metallic hydrogen!) of radius Rc. It is sur- rounded by a spherical cloud of gaseous hydrogen of radius Rg, where Rg > Rc. Let’s assume that the core is of uniform density c and the gaseous cloud is also of uniform density g. What is the gravitational force on an object of mass m that is located at a radius r from the center of Jupiter? Note that you must consider the cases where the object is inside the core, within the gas layer, and outside of the planet. Back to Problem List 5 5 { GRAVITATION Last Updated: July 16, 2012 5.5 Sphere with linearly increasing mass density Given: Pollock { Spring 2011 A planet of mass M and radius R has a nonuniform density that varies with r, the distance from the center according to  = Ar for 0  r  R. (a) What is the constant A in terms of M and R? Does this density pro le strike you as physically plausible, or is just designed as a mathematical exercise? (Brie y, explain) (b) Determine the gravitational force on a satellite of mass m orbiting this planet. In words, please outline the method you plan to use for your solution. (Use the easiest method you can come up with!) In your calculation, you will need to argue that the magnitude of ~g(r; ; ) depends only on r. Be very explicit about this – how do you know that it doesn’t, in fact, depend on  or ? (c) Determine the gravitational force felt by a rock of mass m inside the planet, located at radius r < R. (If the method you use is di erent than in part b, explain why you switched. If not, just proceed!) Explicitly check your result for this part by considering the limits r ! 0 and r ! R. Back to Problem List 6 5 { GRAVITATION Last Updated: July 16, 2012 5.6 Jumping o Vesta Given: Pollock { Spring 2011 You are stranded on the surface of the asteroid Vesta. If the mass of the asteroid is M and its radius is R, how fast would you have to jump o its surface to be able to escape from its gravitational eld? (Your estimate should be based on parameters that characterize the asteroid, not parameters that describe your jumping ability.) Given your formula, look up the approximate mass and radius of the asteroid Vesta 3 and determine a numerical value of the escape velocity. Could you escape in this way? (Brie y, explain) If so, roughly how big in radius is the maximum the asteroid could be, for you to still escape this way? If not, estimate how much smaller an asteroid you would need, to escape from it in this way? Figure 1: Back to Problem List 7 5 { GRAVITATION Last Updated: July 16, 2012 5.7 Gravitational force between two massive rods Given: Pollock { Spring 2011 Consider two identical uniform rods of length L and mass m lying along the same line and having their closest points separated by a distance d as shown in the gure (a) Calculate the mutual force between these rods, both its direction and magnitude. (b) Now do several checks. First, make sure the units worked out (!) The, nd the magnitude of the force in the limit L ! 0. What do you expect? Brie y, discuss. Lastly, nd the magnitude of the force in the limit d ! 1 ? Again, is it what you expect? Brie y, discuss. Figure 2: Given: Pollock { Spring 2012 Determining the gravitational force between two rods: (a) Consider a thin, uniform rod of mass m and length L (and negligible other dimensions) lying on the x axis (from x=-L to 0), as shown in g 1a. Derive a formula for the gravitational eld \g" at any arbitrary point x to the right of the origin (but still on the x-axis!) due to this rod. (b) Now suppose a second rod of length L and mass m sits on the x axis as shown in g 1b, with the left edge a distance \d" away. Calculate the mutual gravitational force between these rods. (c) Let's do some checks! Show that the units work out in parts a and b. Find the magnitude of the force in part a, in the limit x >> L: What do you expect? Brie y, discuss! Finally, verify that your answer to part b gives what you expect in the limit d >> L. ( Hint: This is a bit harder! You need to consistently expand everything to second order, not just rst, because of some interesting cancellations) Fig 1a Fig 1b L m +x x=0 L x=0 x=d m Fig 1a Fig 1b L m +x x=0 L +x x=0 x=d L m m Back to Problem List 8 5 { GRAVITATION Last Updated: July 16, 2012 5.8 Potential energy { Check your answer! Given: Pollock { Spring 2011 On the last exam, we had a problem with a at ring, uniform mass per unit area of , inner radius of R, outer radius of 2R. A satellite (mass m) sat a distance z above the center of the ring. We asked for the gravitational potential energy, and the answer was U(z) = ?2Gm( p 4R2 + z2 ? p R2 + z2) (1) (a) If you are far from the disk (on the z axis), what do you expect for the formula for U(z)? (Don’t say \0″ – as usual, we want the functional form of U(z) as you move far away. Also, explicitly state what we mean by \far away”. (Please don’t compare something with units to something without units!) (b) Show explicitly that the formula above does indeed give precisely the functional dependence you expect. Back to Problem List 9 5 { GRAVITATION Last Updated: July 16, 2012 5.9 Ways of solving gravitational problems Given: Pollock { Spring 2011, Spring 2012 Infinite cylinder ρ=cr x z (a) Half-infinite line mass, uniform linear mass density, λ x (b) R z  P Figure 3: (a) An in nite cylinder of radius R centered on the z-axis, with non-uniform volume mass density  = cr, where r is the radius in cylindrical coordinates. (b) A half-in nite line of mass on the x-axis extending from x = 0 to x = +1, with uniform linear mass density . There are two general methods we use to solve gravitational problems (i.e. nd ~g given some distribution of mass). (a) Describe these two methods. We claim one of these methods is easiest to solve for ~g of mass distribution (a) above, and the other method is easiest to solve for ~g of the mass distribution (b) above. Which method goes with which mass distribution? Please justify your answer. (b) Find ~g of the mass distribution (a) above for any arbitrary point outside the cylinder. (c) Find the x component of the gravitational acceleration, gx, generated by the mass distribution labeled (b) above, at a point P a given distance z up the positive z-axis (as shown). Back to Problem List 10 5 { GRAVITATION Last Updated: July 16, 2012 5.10 Rod with linearly increasing mass density Given: Pollock { Spring 2012 Consider a very (in nitesimally!) thin but massive rod, length L (total mass M), centered around the origin, sitting along the x-axis. (So the left end is at (-L/2, 0,0) and the right end is at (+L/2,0,0) Assume the mass density  (which has units of kg/m)is not uniform, but instead varies linearly with distance from the origin, (x) = cjxj. (a) What is that constant \c” in terms of M and L? What is the direction of the gravitational eld generated by this mass distribution at a point in space a distance z above the center of the rod, i.e. at (0; 0; z) Explain your reasoning for the direction carefully, try not to simply \wave your hands.” (The answer is extremely intuitive, but can you justify that it is correct?) (b) Compute the gravitational eld, ~g, at the point (0; 0; z) by directly integrating Newton’s law of gravity, summing over all in nitesimal \chunks” of mass along the rod. (c) Compute the gravitational potential at the point (0; 0; z) by directly integrating ?Gdm=r, sum- ming over all in nitesimal \chunks” dm along the rod. Then, take the z-component of the gradient of this potential to check that you agree with your result from the previous part. (d) In the limit of large z what do you expect for the functional form for gravitational potential? (Hint: Don’t just say it goes to zero! It’s a rod of mass M, when you’re far away what does it look like? How does it go to zero?) What does \large z” mean here? Use the binomial (or Taylor) expansion to verify that your formula does indeed give exactly what you expect. (Hint: you cannot Taylor expand in something BIG, you have to Taylor expand in something small.) (e) Can you use Gauss’ law to gure out the gravitational potential at the point (0; 0; z)? (If so, do it and check your previous answers. If not, why not?) Back to Problem List 11 5 { GRAVITATION Last Updated: July 16, 2012 5.11 Sphere with constant internal gravitational eld Given: Pollock { Spring 2012 (a) Imagine a planet of total mass M and radius R which has a nonuniform mass density that varies just with r, the distance from the center. For this (admittedly very unusual!) planet, suppose the gravitational eld strength inside the planet turns out to be independent of the radial distance within the sphere. Find the function describing the mass density  = (r) of this planet. (Your nal answer should be written in terms of the given constants.) (b) Now, determine the gravitational force on a satellite of mass m orbiting this planet at distance r > R. (Use the easiest method you can come up with!) Explain your work in words as well as formulas. For instance, in your calculation, you will need to argue that the magnitude of ~g(r; ; ) depends only on r. Be explicit about this – how do you know that it doesn’t, in fact, depend on  or ? (c) As a nal check, explicitly show that your solutions inside and outside the planet (parts a and b) are consistent when r = R. Please also comment on whether this density pro le strikes you as physically plausible, or is it just designed as a mathematical exercise? Defend your reasoning. Back to Problem List 12 5 { GRAVITATION Last Updated: July 16, 2012 5.12 Throwing a rock o the moon Given: Pollock { Spring 2012 Assuming that asteroids have roughly the same mass density as the moon, make an estimate of the largest asteroid that an astronaut could be standing on, and still have a chance of throwing a small object (with their arms, no machinery!) so that it completely escapes the asteroid’s gravitational eld. (This minimum speed is called \escape velocity”) Is the size you computed typical for asteroids in our solar system? Back to Problem List 13

5 { GRAVITATION Last Updated: July 16, 2012 Problem List 5.1 Total mass of a shell 5.2 Tunnel through the moon 5.3 Gravitational eld above the center of a thin hoop 5.4 Gravitational force near a metal-cored planet surrounded by a gaseous cloud 5.5 Sphere with linearly increasing mass density 5.6 Jumping o Vesta 5.7 Gravitational force between two massive rods 5.8 Potential energy { Check your answer! 5.9 Ways of solving gravitational problems 5.10 Rod with linearly increasing mass density 5.11 Sphere with constant internal gravitational eld 5.12 Throwing a rock o the moon These problems are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Un- ported License. Please share and/or modify. Back to Problem List 1 5 { GRAVITATION Last Updated: July 16, 2012 5.1 Total mass of a shell Given: Marino { Fall 2011 Consider a spherical shell that extends from r = R to r = 2R with a non-uniform density (r) = 0r. What is the total mass of the shell? Back to Problem List 2 5 { GRAVITATION Last Updated: July 16, 2012 5.2 Tunnel through the moon Given: Marino { Fall 2011 Imagine that NASA digs a straight tunnel through the center of the moon (see gure) to access the Moon’s 3He deposits. An astronaut places a rock in the tunnel at the surface of the moon, and releases it (from rest). Show that the rock obeys the force law for a mass connected to a spring. What is the spring constant? Find the oscillation period for this motion if you assume that Moon has a mass of 7.351022 kg and a radius of 1.74106 m. Assume the moon’s density is uniform throughout its volume, and ignore the moon’s rotation. Given: Pollock { Spring 2011 Imagine (in a parallel universe of unlimited budgets) that NASA digs a straight tunnel through the center of the moon (see gure). A robot place a rock in the tunnel at position r = r0 from the center of the moon, and releases it (from rest). Use Newton’s second law to write the equation of motion of the rock and solve for r(t). Explain in words the rock’s motion. Does the rock return to its initial position at any later time? If so, how long does it takes to return to it? (Give a formula, and a number.) Assume the moon’s density is uniform throughout its volume, and ignore the moon’s rotation. Given: Pollock { Spring 2012 Now lets consider our (real) planet Earth, with total mass M and radius R which we will approximate as a uniform mass density, (r) = 0. (a) Neglecting rotational and frictional e ects, show that a particle dropped into a hole drilled straight through the center of the earth all the way to the far side will oscillate between the two endpoints. (Hint: you will need to set up, and solve, an ODE for the motion) (b) Find the period of the oscillation of this motion. Get a number (in minutes) as a nal result, using data for the earth’s size and mass. (How does that compare to ying to Perth and back?!) Extra Credit: OK, even with unlimited budgets, digging a tunnel through the center of the earth is preposterous. But, suppose instead that the tunnel is a straight-line \chord” through the earth, say directly from New York to Los Angeles. Show that your nal answer for the time taken does not depend on the location of that chord! This is rather remarkable – look again at the time for a free-fall trip (no energy required, except perhaps to compensate for friction) How long would that trip take? Could this work?! Back to Problem List 3 5 { GRAVITATION Last Updated: July 16, 2012 5.3 Gravitational eld above the center of a thin hoop Given: Pollock { Spring 2011, Spring 2012 Consider a very (in nitesimally!) thin but massive loop, radius R (total mass M), centered around the origin, sitting in the x-y plane. Assume it has a uniform linear mass density  (which has units of kg/m) all around it. (So, it’s like a skinny donut that is mostly hole, centered around the z-axis) (a) What is  in terms of M and R? What is the direction of the gravitational eld generated by this mass distribution at a point in space a distance z above the center of the donut, i.e. at (0; 0; z) Explain your reasoning for the direction carefully, try not to simply \wave your hands.” (The answer is extremely intuitive, but can you justify that it is correct?) (b) Compute the gravitational eld, ~g, at the point (0; 0; z) by directly integrating Newton’s law of gravity, summing over all in nitesimal \chunks” of mass along the loop. (c) Compute the gravitational potential at the point (0; 0; z) by directly integrating ?Gdm=r, sum- ming over all in nitesimal \chunks” dm along the loop. Then, take the z-component of the gradient of this potential to check that you agree with your result from the previous part. (d) In the two separate limits z << R and z >> R, Taylor expand your g- eld (in the z-direction)out only to the rst non-zero term, and convince us that both limits make good physical sense. (e) Can you use Gauss’ law to gure out the gravitational potential at the point (0; 0; z)? (If so, do it and check your previous answers. If not, why not?) Extra credit: If you place a small mass a small distance z away from the center, use your Taylor limit for z << R above to write a simple ODE for the equation of motion. Solve it, and discuss the motion Back to Problem List 4 5 { GRAVITATION Last Updated: July 16, 2012 5.4 Gravitational force near a metal-cored planet surrounded by a gaseous cloud Given: Pollock { Spring 2011 Jupiter is composed of a dense spherical core (of liquid metallic hydrogen!) of radius Rc. It is sur- rounded by a spherical cloud of gaseous hydrogen of radius Rg, where Rg > Rc. Let’s assume that the core is of uniform density c and the gaseous cloud is also of uniform density g. What is the gravitational force on an object of mass m that is located at a radius r from the center of Jupiter? Note that you must consider the cases where the object is inside the core, within the gas layer, and outside of the planet. Back to Problem List 5 5 { GRAVITATION Last Updated: July 16, 2012 5.5 Sphere with linearly increasing mass density Given: Pollock { Spring 2011 A planet of mass M and radius R has a nonuniform density that varies with r, the distance from the center according to  = Ar for 0  r  R. (a) What is the constant A in terms of M and R? Does this density pro le strike you as physically plausible, or is just designed as a mathematical exercise? (Brie y, explain) (b) Determine the gravitational force on a satellite of mass m orbiting this planet. In words, please outline the method you plan to use for your solution. (Use the easiest method you can come up with!) In your calculation, you will need to argue that the magnitude of ~g(r; ; ) depends only on r. Be very explicit about this – how do you know that it doesn’t, in fact, depend on  or ? (c) Determine the gravitational force felt by a rock of mass m inside the planet, located at radius r < R. (If the method you use is di erent than in part b, explain why you switched. If not, just proceed!) Explicitly check your result for this part by considering the limits r ! 0 and r ! R. Back to Problem List 6 5 { GRAVITATION Last Updated: July 16, 2012 5.6 Jumping o Vesta Given: Pollock { Spring 2011 You are stranded on the surface of the asteroid Vesta. If the mass of the asteroid is M and its radius is R, how fast would you have to jump o its surface to be able to escape from its gravitational eld? (Your estimate should be based on parameters that characterize the asteroid, not parameters that describe your jumping ability.) Given your formula, look up the approximate mass and radius of the asteroid Vesta 3 and determine a numerical value of the escape velocity. Could you escape in this way? (Brie y, explain) If so, roughly how big in radius is the maximum the asteroid could be, for you to still escape this way? If not, estimate how much smaller an asteroid you would need, to escape from it in this way? Figure 1: Back to Problem List 7 5 { GRAVITATION Last Updated: July 16, 2012 5.7 Gravitational force between two massive rods Given: Pollock { Spring 2011 Consider two identical uniform rods of length L and mass m lying along the same line and having their closest points separated by a distance d as shown in the gure (a) Calculate the mutual force between these rods, both its direction and magnitude. (b) Now do several checks. First, make sure the units worked out (!) The, nd the magnitude of the force in the limit L ! 0. What do you expect? Brie y, discuss. Lastly, nd the magnitude of the force in the limit d ! 1 ? Again, is it what you expect? Brie y, discuss. Figure 2: Given: Pollock { Spring 2012 Determining the gravitational force between two rods: (a) Consider a thin, uniform rod of mass m and length L (and negligible other dimensions) lying on the x axis (from x=-L to 0), as shown in g 1a. Derive a formula for the gravitational eld \g" at any arbitrary point x to the right of the origin (but still on the x-axis!) due to this rod. (b) Now suppose a second rod of length L and mass m sits on the x axis as shown in g 1b, with the left edge a distance \d" away. Calculate the mutual gravitational force between these rods. (c) Let's do some checks! Show that the units work out in parts a and b. Find the magnitude of the force in part a, in the limit x >> L: What do you expect? Brie y, discuss! Finally, verify that your answer to part b gives what you expect in the limit d >> L. ( Hint: This is a bit harder! You need to consistently expand everything to second order, not just rst, because of some interesting cancellations) Fig 1a Fig 1b L m +x x=0 L x=0 x=d m Fig 1a Fig 1b L m +x x=0 L +x x=0 x=d L m m Back to Problem List 8 5 { GRAVITATION Last Updated: July 16, 2012 5.8 Potential energy { Check your answer! Given: Pollock { Spring 2011 On the last exam, we had a problem with a at ring, uniform mass per unit area of , inner radius of R, outer radius of 2R. A satellite (mass m) sat a distance z above the center of the ring. We asked for the gravitational potential energy, and the answer was U(z) = ?2Gm( p 4R2 + z2 ? p R2 + z2) (1) (a) If you are far from the disk (on the z axis), what do you expect for the formula for U(z)? (Don’t say \0″ – as usual, we want the functional form of U(z) as you move far away. Also, explicitly state what we mean by \far away”. (Please don’t compare something with units to something without units!) (b) Show explicitly that the formula above does indeed give precisely the functional dependence you expect. Back to Problem List 9 5 { GRAVITATION Last Updated: July 16, 2012 5.9 Ways of solving gravitational problems Given: Pollock { Spring 2011, Spring 2012 Infinite cylinder ρ=cr x z (a) Half-infinite line mass, uniform linear mass density, λ x (b) R z  P Figure 3: (a) An in nite cylinder of radius R centered on the z-axis, with non-uniform volume mass density  = cr, where r is the radius in cylindrical coordinates. (b) A half-in nite line of mass on the x-axis extending from x = 0 to x = +1, with uniform linear mass density . There are two general methods we use to solve gravitational problems (i.e. nd ~g given some distribution of mass). (a) Describe these two methods. We claim one of these methods is easiest to solve for ~g of mass distribution (a) above, and the other method is easiest to solve for ~g of the mass distribution (b) above. Which method goes with which mass distribution? Please justify your answer. (b) Find ~g of the mass distribution (a) above for any arbitrary point outside the cylinder. (c) Find the x component of the gravitational acceleration, gx, generated by the mass distribution labeled (b) above, at a point P a given distance z up the positive z-axis (as shown). Back to Problem List 10 5 { GRAVITATION Last Updated: July 16, 2012 5.10 Rod with linearly increasing mass density Given: Pollock { Spring 2012 Consider a very (in nitesimally!) thin but massive rod, length L (total mass M), centered around the origin, sitting along the x-axis. (So the left end is at (-L/2, 0,0) and the right end is at (+L/2,0,0) Assume the mass density  (which has units of kg/m)is not uniform, but instead varies linearly with distance from the origin, (x) = cjxj. (a) What is that constant \c” in terms of M and L? What is the direction of the gravitational eld generated by this mass distribution at a point in space a distance z above the center of the rod, i.e. at (0; 0; z) Explain your reasoning for the direction carefully, try not to simply \wave your hands.” (The answer is extremely intuitive, but can you justify that it is correct?) (b) Compute the gravitational eld, ~g, at the point (0; 0; z) by directly integrating Newton’s law of gravity, summing over all in nitesimal \chunks” of mass along the rod. (c) Compute the gravitational potential at the point (0; 0; z) by directly integrating ?Gdm=r, sum- ming over all in nitesimal \chunks” dm along the rod. Then, take the z-component of the gradient of this potential to check that you agree with your result from the previous part. (d) In the limit of large z what do you expect for the functional form for gravitational potential? (Hint: Don’t just say it goes to zero! It’s a rod of mass M, when you’re far away what does it look like? How does it go to zero?) What does \large z” mean here? Use the binomial (or Taylor) expansion to verify that your formula does indeed give exactly what you expect. (Hint: you cannot Taylor expand in something BIG, you have to Taylor expand in something small.) (e) Can you use Gauss’ law to gure out the gravitational potential at the point (0; 0; z)? (If so, do it and check your previous answers. If not, why not?) Back to Problem List 11 5 { GRAVITATION Last Updated: July 16, 2012 5.11 Sphere with constant internal gravitational eld Given: Pollock { Spring 2012 (a) Imagine a planet of total mass M and radius R which has a nonuniform mass density that varies just with r, the distance from the center. For this (admittedly very unusual!) planet, suppose the gravitational eld strength inside the planet turns out to be independent of the radial distance within the sphere. Find the function describing the mass density  = (r) of this planet. (Your nal answer should be written in terms of the given constants.) (b) Now, determine the gravitational force on a satellite of mass m orbiting this planet at distance r > R. (Use the easiest method you can come up with!) Explain your work in words as well as formulas. For instance, in your calculation, you will need to argue that the magnitude of ~g(r; ; ) depends only on r. Be explicit about this – how do you know that it doesn’t, in fact, depend on  or ? (c) As a nal check, explicitly show that your solutions inside and outside the planet (parts a and b) are consistent when r = R. Please also comment on whether this density pro le strikes you as physically plausible, or is it just designed as a mathematical exercise? Defend your reasoning. Back to Problem List 12 5 { GRAVITATION Last Updated: July 16, 2012 5.12 Throwing a rock o the moon Given: Pollock { Spring 2012 Assuming that asteroids have roughly the same mass density as the moon, make an estimate of the largest asteroid that an astronaut could be standing on, and still have a chance of throwing a small object (with their arms, no machinery!) so that it completely escapes the asteroid’s gravitational eld. (This minimum speed is called \escape velocity”) Is the size you computed typical for asteroids in our solar system? Back to Problem List 13