solution20_pdf - arellano(aa39398 Homework 14...

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arellano (aa39398) – Homework 14 – weathers – (17101) 1 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page – fnd 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 65 cm apart on the same axle. ±rom the angular displacement 21 . 5 oF the two bul- let holes in the disks and the rotational speed 1262 rev / min oF the disks, we can determine the speed oF the bullet. 21 . 5 v 1262 rev / min 65 cm What is the speed oF the bullet? Correct answer: 228 . 921 m / s. Explanation: Let : ω = 1262 rev / min , d = 65 cm , and θ = 21 . 5 . θ = ω t t = θ ω , so the speed oF the bullet is v = d t = d ω θ = (65 cm) (1262 rev / min) 21 . 5 × 360 1 rev 1 m 100 cm 1 min 60 s = 228 . 921 m / s . keywords: 002 10.0 points A wheel starts From rest at t = 0 and rotates with a constant angular acceleration about a fxed axis. It completes the frst revolution in 5 . 3 s. How long aFter t = 0 will the wheel com- plete the second revolution? Correct answer: 7 . 49533 s. Explanation: Let : t 1 = 5 . 3 s , θ 1 = 1 rev , and θ 2 = 2 rev . The wheel starts From rest, so θ = θ 0 + 1 2 αt 2 = 1 2 α t 2 t 2 . Thus θ 2 θ 1 = t 2 2 t 2 1 t 2 = r θ 2 θ 1 t 1 = r 2 rev 1 rev (5 . 3 s) = 7 . 49533 s . 003 10.0 points A bicycle is turned upside down while its owner repairs a ²at tire. A Friend spins the other wheel oF radius 0 . 4 m and observes that drops oF water ²y o³ tangentially. She mea- sures the height reached by drops moving ver- tically. A drop that breaks loose From the tire on one turn rises 44 . 1 cm above the tangent point. A drop that breaks loose on the next turn rises 41 . 3 cm above the tangent point
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arellano (aa39398) – Homework 14 – weathers – (17101) 2 (the angular speed of the wheel is decreas- ing). h 0 . 4 m radius ω Find the angular deceleration of the wheel. The acceleration of gravity is 9 . 8 m / s 2 . As- sume the angular deceleration is constant. Correct answer: 0
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solution20_pdf - arellano(aa39398 Homework 14...

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