Spring 2010 - HW13_Solution - banuelos (ojb93) Homework 13...

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Unformatted text preview: banuelos (ojb93) Homework 13 florin (58140) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points The speed of a moving bullet can be deter- mined by allowing the bullet to pass through two rotating paper disks mounted a distance 98 cm apart on the same axle. From the angular displacement 15 . 4 of the two bul- let holes in the disks and the rotational speed 990 rev / min of the disks, we can determine the speed of the bullet. 15 . 4 v 990 rev / min 98 cm What is the speed of the bullet? Correct answer: 378 m / s. Explanation: Let : = 990 rev / min , d = 98 cm , and = 15 . 4 . = t t = , so the speed of the bullet is v = d t = d = (98 cm) (990 rev / min) 15 . 4 360 1 rev 1 m 100 cm 1 min 60 s = 378 m / s . keywords: 002 10.0 points A bug is on the rim of a 78 rev / min, 12 in . diameter record. The record moves from rest to its final angular speed in 2 . 71 s. Find the bugs centripetal acceleration 1 . 5 s after the bug starts from rest. (1 in = 2.54 cm). Correct answer: 3 . 11513 m / s 2 . Explanation: Let : w = 78 rev / min , t = 2 . 71 s , r = 6 in , and t = 1 . 5 s . = t , so = t = t t = 78 rev / min 2 . 71 s (1 . 5 s) 1 min 60 s = 4 . 52111 rad / s , and a r = v 2 t r = r 2 = (6 in)(4 . 52111 rad / s) 2 1 cm 2 . 54 in 1 m 100 cm = 3 . 11513 m / s 2 . 003 10.0 points A small wheel of radius 1 . 5 cm drives a large wheel of radius 12 . 9 cm by having their cir- cumferences pressed together. If the small wheel turns at 514 rad / s, how fast does the larger one turn?...
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Spring 2010 - HW13_Solution - banuelos (ojb93) Homework 13...

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