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Homework 19

# Homework 19 - sanchez(ds28677 homework 19 Turner(58220 This...

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sanchez (ds28677) – homework 19 – Turner – (58220) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points What velocity must a car with a mass of 1270 kg have in order to have the same mo- mentum as a 2260 kg pickup truck traveling at 26 m / s to the east? Correct answer: 46 . 2677 m / s. Explanation: Let : m 1 = 1270 kg , m 2 = 2260 kg , and v 2 = 26 m / s to the east . vectorp = m 1 vectorv 1 = m 2 vectorv 2 v 1 = m 2 v 2 m 1 = (2260 kg) (26 m / s) 1270 kg = 46 . 2677 m / s to the east. 002 10.0 points Note: Take East as the positive direction. A(n) 86 kg fisherman jumps from a dock into a 122 kg rowboat at rest on the West side of the dock. If the velocity of the fisherman is 5 . 1 m / s to the West as he leaves the dock, what is the final velocity of the fisherman and the boat? Correct answer: 2 . 10865 m / s. Explanation: Let West be negative: Let : m 1 = 86 kg kg , m 2 = 122 kg kg , and v i, 1 = 5 . 1 m / s m / s . The boat and fisherman have the same final speed, and v i, 2 = 0 m/s, so m 1 vectorv i, 1 + m 2 vectorv i, 2 = ( m 1 + m 2 ) vectorv f m 1 vectorv i, 1 = ( m 1 + m 2 ) vectorv f v f = m 1 v i m 1 + m 2 = (86 kg) ( 5 . 1 m / s) 86 kg + 122 kg = 2 . 10865 m / s , which is 2 . 10865 m / s to the West. 003 10.0 points A(n) 666 N man stands in the middle of a frozen pond of radius 7 . 4 m. He is un- able to get to the other side because of a lack of friction between his shoes and the ice. To overcome this difficulty, he throws his 1 . 2 kg physics textbook horizontally toward the north shore, at a speed of 6 . 7 m / s. The acceleration of gravity is 9 . 81 m / s 2 . How long does it take him to reach the south shore? Correct answer: 62 . 4857 s. Explanation: Let : W m = 666 N , r = 7 . 4 m , m b = 1 . 2 kg , and v b = 6 . 7 m / s . The mass of the man is m m = W m g . From conservation of momentum, m m v m + m b v b = m m v m + m b v b 0 = m m v m + m b v b v m = m b m m v b = g m b W m v b = ( 9 . 81 m / s 2 ) (1 . 2 kg) 666 N (6 . 7 m / s) = 0 . 118427 m / s .

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sanchez (ds28677) – homework 19 – Turner – (58220) 2 The time to travel the 7 . 4 m to shore is t = Δ x | v m | = 7 . 4 m 0 . 118427 m / s = 62 . 4857 s . 004 10.0 points An 58 kg object moving to the right at 42 . 2 cm / s overtakes and collides elastically with a second 38 . 4 kg object moving in the same direction at 24 . 4 cm / s. Find the velocity of the second object after the collision.
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