solution 8

# solution 8 - reyes(mr29667 – Homework 8 – chelikowsky...

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Unformatted text preview: reyes (mr29667) – Homework 8 – chelikowsky – (59005) 1 This print-out should have 18 questions. Multiple-choice 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 α 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 α 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 α = 1 . 74 × 10 7 m / s , M α = 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 α vectorv α + 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 α particle with speed bardbl vectorv Th bardbl = bardbl vectorv α bardbl M α 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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## This note was uploaded on 07/24/2010 for the course PHY 59005 taught by Professor Chelikowsky during the Fall '09 term at University of Texas.

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solution 8 - reyes(mr29667 – Homework 8 – chelikowsky...

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