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Audra Bradford
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1 Feedback Potential Energy II You submitted this quiz on Fri 5 Jul :38 AM PDT (UTC -0700). You got a score of 5.00 out of You can attempt again, if you'd like. Some questions provided by Matter and Interactions (3rd. Ed.), R. Chabay & B. Sherwood. Copyright (2010, John Wiley & Sons). This material is used by permission of John Wiley & Sons, Inc. Question 1 The radius of Mercury (from the center to just above the atmosphere) is 2440 km ( m), and its mass is atmosphere of Mercury kg. An object is launched straight up from just above the What initial speed is needed so that when the object is far from Mercury its final speed is 1000 m/s? Answer in m/s Answer : [4170,4190] 1/9

2 Question 2 What initial speed is needed so that when the object is far from Mercury its final speed is 0 m/s? (This is called the "escape speed.") Answer in m/s Total 1.00 / 1.00 Answer : [4040,4070] Question 3 The diagram below is a graph of the energy of a system of a planet interacting with a star. The gravitational potential energy U g is shown as the thick curve, and plotted along the vertical axis K + U g are various values of. 2/9

3 Suppose that energy of the system, are true? K + U g, is equal to A. Which of the following statements The kinetic energy of the system is greater when the distance between the star and planet is r1 than when the distance between the two bodies is r2. When the separation between the two bodies is r2, the kinetic energy of the system is (B - C) The planet will escape The system is a bound system; the planet can never escape The potential energy of the system decreases as the planet moves from r1 to r2. When the separation between the two bodies is r2, the kinetic energy of the system is (A - B) Total 1.00 / /9

4 Answer : -The kinetic energy of the system is greater when the distance between the star and planet is r1 than when the distance between the two bodies is r2. -When the separation between the two bodies is r2, the kinetic energy of the system is (A - B). -The system is a bound system; the planet can never escape. Question 4 Suppose instead that the energy, true? K + U g, is equal to B. Which of the following statements are When the separation between the planet and star is r2, the kinetic energy of the system is zero The planet and star cannot get farther apart than r This is not a bound system; the planet can escape When the separation between the planet and star is r2, the potential energy of the system is zero Total 1.00 / 1.00 Answer : -The planet and star cannot get farther apart than r2. -When the separation between the planet and star is r2, the kinetic energy of the system is zero. 4/9

5 Question 5 The diagram above shows the path of a comet orbiting a star. You will be asked to rank order various quantities in terms of their values at the locations marked on the path, with the largest first. You can use the symbols ">" and "=". For example, if you were asked to rank order the locations in terms of their distance from the star, largest first, you would type: "A>B>C>D>E" Note: Do not include spaces. Otherwise your answer may be graded improperly. Rank order the locations on the path in terms of the magnitude of the comet's momentum at each location, starting with the location where the magnitude of the momentum is the largest: A=B=C=D=E A=B=C=D=E 0.00 Answer : E>D>C>B>A Question 6 5/9

6 Rank order the locations on the path in terms of the comet's kinetic energy at each location, starting with the location where the kinetic energy is the largest: A>B>C>D>E A>B>C>D>E 0.00 Answer : E>D>C>B>A Question 7 Consider the system of the comet plus the star. Which of the following statements are correct? As the comet slows down, the kinetic energy of the system decreases. External work must be done on the system to speed up the comet. As the comet slows down, energy is lost from the system. As the kinetic energy of the system increases, the gravitational potential energy of the system decreases. 6/9

7 As the comet's kinetic energy increases, the gravitational potential energy of the system also increases. Total 1.00 / 1.00 Answer : -As the kinetic energy of the system increases, the gravitational potential energy of the system decreases. -As the comet slows down, the kinetic energy of the system decreases. Question 8 Still Consider the system of the comet plus the star. Which of the following statements are also correct? Along this path the gravitational potential energy of the system is never zero. The sum of the kinetic energy of the system plus the gravitational potential energy of the system is a positive number. The sum of the kinetic energy of the system plus the gravitational potential energy of the system is the same at every location along this path. At every location along the comet's path the gravitational potential energy of the system is negative. The gravitational potential energy of the system is inversely proportional to the square of the distance between the comet and star. 7/9

8 Total 1.00 / 1.00 Answer : -At every location along the comet's path the gravitational potential energy of the system is negative. -Along this path the gravitational potential energy of the system is never zero. -The sum of the kinetic energy of the system plus the gravitational potential energy of the system is the same at every location along this path. Question 9 Rank order the locations on the path in terms of the potential energy of the system at each location, largest first. (Remember that -3 > -5). Note: Do not include spaces in your answer. Otherwise your answer may be graded improperly. E>D>C>B>A E>D>C>B>A 0.00 Answer : A>B>C>D>E 8/9

9 Question 10 Consider an isolated system, by which we mean a system free of external forces. If the sum of the particle energies in the system increases by 150 J, what must have been the change in the system's potential energy,? Answer in J. ΔU Answer : /9

Feedback Point Particle & Multiparticle (Real) Models: Part 2

Feedback Point Particle & Multiparticle (Real) Models: Part 2 You submitted this quiz on Sat 20 Jul 2013 1:01 PM PDT (UTC -0700). You got a score of 26.50 out of 27.00. You can attempt again, if you'd