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1169060711Xuj - Alvarado Patrick Homework 1 Due 10:00 am...

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Alvarado, Patrick – Homework 1 – Due: Sep 14 2006, 10:00 am – Inst: Andrei Sirenko 1 This print-out should have 19 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 2) 10 points A record has an angular speed of 50 . 4 rev / min. What is its angular speed? Correct answer: 5 . 27788 rad / s. Explanation: 1 rev = 6 . 28319 rad, and 1 min = 60 s , Therefore, ω 1 = (50 . 4 rev / min) 2 π rad rev 1 min 60 s = 5 . 27788 rad / s . 002 (part 2 of 2) 10 points Through what angle, in radians, does it rotate in 0 . 932 s? Correct answer: 4 . 91898 rad. Explanation: θ = ω t = (5 . 27788 rad / s) (0 . 932 s) = 4 . 91898 rad . keywords: 003 (part 1 of 1) 10 points A large wheel is coupled to a wheel with half the diameter as shown. r 2 r How does the rotational speed of the smaller wheel compare with that of the larger wheel? How do the tangential speeds at the rims compare (assuming the belt doesn’t slip)? 1. The smaller wheel has four times the ro- tational speed and the same tangential speed as the larger wheel. 2. The smaller wheel has twice the rotational speed and the same tangential speed as the larger wheel. correct 3. The smaller wheel has half the rotational speed and half the tangential speed as the larger wheel. 4. The smaller wheel has twice the rotational speed and twice the tangential speed as the larger wheel. Explanation: v = r ω The tangential speeds are equal, since the rims are in contact with the belt and have the same linear speed as the belt. The smaller wheel (with half the radius) rotates twice as fast: 1 2 r (2 ω ) = r ω = v keywords: 004 (part 1 of 1) 10 points Harry and Sue cycle at the same speed. The tires on Harry’s bike have a larger diameter than those on Sue’s bike. Which tires have the greater rotational speed? 1. Sue’s tires correct 2. The rotational speeds are the same. 3. It depends on the speed. 4. Harry’s tires Explanation:
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Alvarado, Patrick – Homework 1 – Due: Sep 14 2006, 10:00 am – Inst: Andrei Sirenko 2 v = r ω . Tires with a smaller radius needs a larger rotational speed to obtain the same linear speed. keywords: 005 (part 1 of 1) 10 points A rigid circular wheel spins at constant angu- lar velocity about a stationary axis. Choose the picture below that correctly describes the relative magnitudes and directions of the ve- locity vector of points on the wheel.
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