HW 09 solution - gutierrez (ig3472) HW9 ditmire (58216) 1...

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Unformatted text preview: gutierrez (ig3472) HW9 ditmire (58216) 1 This print-out should have 15 questions. Multiple-choice 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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HW 09 solution - gutierrez (ig3472) HW9 ditmire (58216) 1...

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