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Unformatted text preview: gutierrez (ig3472) HW9 ditmire (58216) 1 This printout should have 15 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points What angular acceleration is necessary to in crease the angular speed of a fan blade from 8.2 rad/s to 15.7 rad/s in 5.3 s? Correct answer: 1 . 41509 rad / s 2 . Explanation: Let : o = 8 . 2 rad / s , f = 15 . 7 rad / s , and t = 5 . 3 s . avg = f o t = 15 . 7 rad / s 8 . 2 rad / s 5 . 3 s = 1 . 41509 rad / s 2 . keywords: 002 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 90 cm apart on the same axle. From the angular displacement 28 . 8 of the two bul let holes in the disks and the rotational speed 1164 rev / min of the disks, we can determine the speed of the bullet. 28 . 8 v 1164 rev / min 90 cm What is the speed of the bullet? Correct answer: 218 . 25 m / s. Explanation: Let : = 1164 rev / min , d = 90 cm , and = 28 . 8 . = t t = , so the speed of the bullet is v = d t = d = (90 cm) (1164 rev / min) 28 . 8 360 1 rev 1 m 100 cm 1 min 60 s = 218 . 25 m / s . keywords: 003 (part 1 of 2) 10.0 points An electric motor rotating a workshop grind ing wheel at a rate of 66 rev / min is switched off with a constant deceleration of 2 . 45 rad / s 2 . How long does it take for the grinding wheel to stop? Correct answer: 2 . 82102 s. Explanation: Let : = 66 rev / min and = 2 . 45 rad / s 2 . Since f = 0 rev/s, f = + t t = f = = 66 rev / min 2 . 45 rad / s 2 2 1 rev 1 min 60 s = 2 . 82102 s . gutierrez (ig3472) HW9 ditmire (58216) 2 004 (part 2 of 2) 10.0 points Through how many radians has the wheel turned during the deceleration? Correct answer: 9 . 74875 rad. Explanation: = t = f + 2 t = 2 t = (66 rev / min) (2 . 82102 s) 2 2 1 rev 1 min 60 s = 9 . 74875 rad ....
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 Spring '08
 Turner
 Physics, Acceleration

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