13 - roofner (bar784) Homework 13 Weathers (17104) This...

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roofner (bar784) – Homework 13 – Weathers – (17104) 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 77 cm apart on the same axle. ±rom the angular displacement 15 . 5 of the two bul- let holes in the disks and the rotational speed 1201 rev / min of the disks, we can determine the speed of the bullet. 15 . 5 v 1201 rev / min 77 cm What is the speed of the bullet? Correct answer: 357 . 975 m / s. Explanation: Let : ω = 1201 rev / min , d = 77 cm , and θ = 15 . 5 . θ = ω t t = θ ω , so the speed of the bullet is v = d t = d ω θ = (77 cm) (1201 rev / min) 15 . 5 × 360 1 rev 1 m 100 cm 1 min 60 s = 357 . 975 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 . 5 s. How long after t = 0 will the wheel com- plete the second revolution? Correct answer: 7 . 77817 s. Explanation: Let : t 1 = 5 . 5 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 . 5 s) = 7 . 77817 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 66 . 4 cm above the tangent point. A drop that breaks loose on the next turn rises 63 . 4 cm above the tangent point (the angular speed of the wheel is decreas- ing).
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roofner (bar784) – Homework 13 – Weathers – (17104) 2 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: 29
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13 - roofner (bar784) Homework 13 Weathers (17104) This...

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