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Unformatted text preview: pels (kcp389) Homework 5 hill (666) 1 This printout should have 36 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 3) 10.0 points The moon has a mass of 7 . 4 10 22 kg and completes an orbit of radius 3 . 8 10 8 m about every 28 days. The Earth has a mass of 6 10 24 kg and completes an orbit of radius 1 . 5 10 11 m every year. What is the speed of the Moon in its orbit? Correct answer: 986 . 442 m / s. Explanation: Let : r 1 = 3 . 8 10 8 m and t 1 = 28 days . The speed of the Moon is v = s t = 2 r 1 t 1 = 2 (3 . 8 10 8 m) 28 days day 24 h h 3600 s = 986 . 442 m / s . 002 (part 2 of 3) 10.0 points What is the kinetic energy of the Moon in orbit? Correct answer: 3 . 60035 10 28 J. Explanation: Let : m 1 = 7 . 4 10 22 kg and v 1 = 986 . 442 m / s . The kinetic energy of the Moon is K 1 = 1 2 m 1 v 2 1 = 1 2 (7 . 4 10 22 kg) (986 . 442 m / s) 2 = 3 . 60035 10 28 J . 003 (part 3 of 3) 10.0 points What is the kinetic energy of the Earth? Correct answer: 2 . 67676 10 33 J. Explanation: Let : r 2 = 1 . 5 10 11 m , t 2 = 1 year , and m 2 = 6 10 24 kg . The speed of the Earth is v 2 = s t = 2 r 2 t 2 = 2 (1 . 5 10 11 m) 1 year year 365 d d 24 h h 3600 s = 29870 . 6 m / s . The kinetic energy of the Earth is K 2 = 1 2 m 2 v 2 2 = 1 2 (6 10 24 kg) (29870 . 6 m / s) 2 = 2 . 67676 10 33 J . 004 10.0 points Which of the two object shown below has the greatest kinetic energy? A m B 1 2 m v 2 v 1. B correct 2. A 3. Unable to determine. 4. Kinetic energies are the same. Explanation: For mass A, K A = 1 2 mv 2 . pels (kcp389) Homework 5 hill (666) 2 For mass B, K B = 1 2 parenleftbigg 1 2 m parenrightbigg (2 v ) 2 = mv 2 . So B has more kinetic energy. 005 10.0 points Which of the following is the best example of kinetic energy? 1. a tornado correct 2. a television set 3. a tank of gasoline 4. a loaded gun 5. a strawberry shortcake 6. a calculator battery 7. a piece of chewing gum 8. a Jolt Cola 9. a stick of dynamite 10. boulder dam Explanation: Kinetic energy is the energy of motion. The only system that is in motion is the tornado. 006 (part 1 of 2) 10.0 points A simple Atwoods machine uses two masses m 1 and m 2 . Starting from rest, the speed of the two masses is 9 . 3 m / s at the end of 6 . 7 s. At that time, the kinetic energy of the system is 51 J and each mass has moved a distance of 31 . 155 m. The acceleration of gravity is 9 . 81 m / s 2 . 31 . 155 m m 1 m 2 Find the value of heavier mass. Correct answer: 0 . 673098 kg. Explanation: Let : v = 9 . 3 m / s , t = 6 . 7 s , K = 51 J , = 31 . 155 m , and g = 9 . 81 m / s 2 ....
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This note was uploaded on 11/30/2008 for the course PHY 2048 taught by Professor Guzman during the Fall '08 term at FAU.
 Fall '08
 Guzman
 Physics, Mass, Work

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