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Unformatted text preview: reyes (mr29667) Homework 8 chelikowsky (59005) 1 This printout should have 18 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 4) 10.0 points Calculate the momentum for a 0 . 3 kg rifle bullet traveling 200 m / s. Correct answer: 60 kg m / s. Explanation: Let : m = 0 . 3 kg and v = 200 m / s . p = mv = (0 . 3 kg)(200 m / s) = 60 kg m / s . 002 (part 2 of 4) 10.0 points What momentum does a 900 kg automobile traveling 0 . 4 m / s (a few miles per hour) have? Correct answer: 360 kg m / s. Explanation: Let : m = 900 kg , and v = 0 . 4 m / s . p = (900 kg)(0 . 4 m / s) = 360 kg m / s . 003 (part 3 of 4) 10.0 points What momentum does a 50 kg person running 12 m / s (a fast sprint) have? Correct answer: 600 kg m / s. Explanation: Let : m = 50 kg , and v = 12 m / s . p = (50 kg)(12 m / s) = 600 kg m / s . 004 (part 4 of 4) 10.0 points What momentum does a 13000 kg truck trav eling 0 . 02 m / s (a slow roll) have? Correct answer: 260 kg m / s. Explanation: Let : m = 13000 kg , and v = 0 . 02 m / s . p = (13000 kg)(0 . 02 m / s) = 260 kg m / s . 005 10.0 points A uranium nucleus 238 U may stay in one piece for billions of years, but sooner or later it de cays into an particle of mass 6 . 64 10 27 kg and 234 Th nucleus of mass 3 . 88 10 25 kg, and the decay process itself is extremely fast (it takes about 10 20 s). Suppose the uranium nucleus was at rest just before the decay. If the particle is emitted at a speed of 1 . 74 10 7 m / s, what would be the recoil speed of the thorium nucleus? Correct answer: 2 . 97773 10 5 m / s. Explanation: Let : v = 1 . 74 10 7 m / s , M = 6 . 64 10 27 kg , and M Th = 3 . 88 10 25 kg . Use momentum conservation: Before the de cay, the Uranium nucleus had zero momentum (it was at rest), and hence the net momentum vector of the decay products should total to zero: vector P tot = M vectorv + M Th vectorv Th = 0 . reyes (mr29667) Homework 8 chelikowsky (59005) 2 This means that the Thorium nucleus recoils in the direction exactly opposite to that of the particle with speed bardbl vectorv Th bardbl = bardbl vectorv bardbl M M Th = (1 . 74 10 7 m / s) (6 . 64 10 27 kg) 3 . 88 10 25 kg = 2 . 97773 10 5 m / s . 006 10.0 points A circular hole of diameter 29 . 9 cm is cut out of a uniform square of sheet metal having sides 59 . 8 cm, as in the figure. d l l What is the distance between the center of mass and the center of the square?...
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 Fall '09
 Chelikowsky

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