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Unformatted text preview: yang (ey942) HW08 TSOI (58160) 1 This printout should have 24 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 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. 1. 2. 3. 4. 5. correct 6. 7. 8. Explanation: Any point on the wheel travels in a circle around the axis, so the velocities of all points are directed parallel to tangents to the wheel. The wheel is rigid, so all points on the wheel travel with the same angular velocity. v = r so the points farther from the axis travel faster than the points closer to the axis. keywords: 002 (part 1 of 4) 10.0 points A potters wheel of radius 16 cm starts from rest and rotates with constant angular accel eration until at the end of 29 s it is moving with angular velocity of 12 rad / s. What is the angular acceleration? Correct answer: 0 . 413793 rad / s 2 . Explanation: Let : = 12 rad / s , = 0 , and t = 29 s . Since the angular acceleration is constant, = t = t = 12 rad / s 29 s = . 413793 rad / s 2 . 003 (part 2 of 4) 10.0 points What is the linear velocity of a point on the rim at the end of the 29 s? yang (ey942) HW08 TSOI (58160) 2 Correct answer: 1 . 92 m / s. Explanation: Let : r = 16 cm = 0 . 16 m . v = r = (12 rad / s) (0 . 16 m) = 1 . 92 m / s . 004 (part 3 of 4) 10.0 points What is the average angular velocity of the wheel during the 29 s? Correct answer: 6 rad / s. Explanation: = + 2 = 2 = 12 rad / s 2 = 6 rad / s . 005 (part 4 of 4) 10.0 points Through what angle did the wheel rotate in the 29 s? Correct answer: 174 rad. Explanation: = t = (6 rad / s) (29 s) = 174 rad . Alternate Solution : = + t + 1 2 t 2 = 1 2 t 2 = 1 2 (0 . 413793 rad / s 2 ) (29 s) 2 = 174 rad . 006 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 92 cm apart on the same axle. From the angular displacement 34 . 5 of the two bul let holes in the disks and the rotational speed 452 rev / min of the disks, we can determine the speed of the bullet. 34 . 5 v 452 rev / min 92 cm What is the speed of the bullet? Correct answer: 72 . 32 m / s. Explanation: Let : = 452 rev / min , d = 92 cm , and = 34 . 5 . = t t = , so the speed of the bullet is v = d t = d = (92 cm) (452 rev / min) 34 . 5 360 1 rev 1 m 100 cm 1 min 60 s = 72 . 32 m / s . keywords: 007 (part 1 of 2) 10.0 points A grinding wheel, initially at rest, is ro tated with constant angular acceleration of 2 . 59 rad / s 2 for 9 . 34 s. The wheel is then brought to rest with uniform deceleration in 13 . 3 rev....
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This note was uploaded on 11/21/2010 for the course PHY 58160 taught by Professor Tsio during the Fall '10 term at University of Texas at Austin.
 Fall '10
 TSIO

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