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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 : ω o = 8 . 2 rad / s , ω f = 15 . 7 rad / s , and Δ t = 5 . 3 s . α avg = ω f ω o Δ 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 : ω = 1164 rev / min , d = 90 cm , and θ = 28 . 8 ◦ . θ = ω t t = θ ω , so the speed of the bullet is v = d t = dω θ = (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 : ω = 66 rev / min and α = 2 . 45 rad / s 2 . Since ω f = 0 rev/s, ω f = ω + α t t = ω f ω α = ω α = 66 rev / min 2 . 45 rad / s 2 2 π 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: θ = ω t = ω f + ω 2 t = ω 2 t = (66 rev / min) (2 . 82102 s) 2 2 π 1 rev × 1 min 60 s = 9 . 74875 rad ....
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 Spring '08
 Turner
 Physics, Acceleration, Kinetic Energy, Mass, Moment Of Inertia, kg, Gutierrez

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