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Unformatted text preview: ouseph (jao888) HW06 tsoi (92940) 1 This printout should have 22 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A record has an angular speed of 19 rev / min. What is its angular speed? Correct answer: 1 . 98968 rad / s. Explanation: Let : = 19 rev / min . = (19 rev / min) parenleftbigg 2 rad rev parenrightbiggparenleftbigg 1 min 60 s parenrightbigg = 1 . 98968 rad / s . 002 (part 2 of 2) 10.0 points Through what angle does it rotate in 0 . 94 s? Correct answer: 1 . 8703 rad. Explanation: Let : t = 0 . 94 s . = t = (1 . 98968 rad / s) (0 . 94 s) = 1 . 8703 rad . 003 (part 1 of 2) 10.0 points A racing car travels on a circular track of radius 310 m, moving with a constant linear speed of 70 . 9 m / s. Find its angular speed. Correct answer: 0 . 22871 rad / s. Explanation: Let : v = 70 . 9 m / s and R = 310 m . The linear speed is v = R = v R = 70 . 9 m / s 310 m = . 22871 rad / s . 004 (part 2 of 2) 10.0 points Find the magnitude of its acceleration. Correct answer: 16 . 2155 m / s 2 . Explanation: With the car moving at a constant speed, there is no tangential acceleration, so the ac celeration is purely radial: a r = v 2 R = (70 . 9 m / s) 2 310 m = 16 . 2155 m / s 2 . 005 10.0 points Initially a wheel rotating about a fixed axis at a constant angular deceleration of 0 . 6 rad / s 2 has an angular velocity of 0 rad / s and an angular position of 9 . 5 rad. What is the angular position of the wheel after 2 . 9 s? Correct answer: 6 . 977 rad. Explanation: Let : = . 6 rad / s 2 , = 0 rad / s , = 9 . 5 rad , and t = 2 . 9 s . From kinematics, = t + 1 2 t 2 + = (0 rad / s) (2 . 9 s) + 1 2 ( . 6 rad / s 2 ) (2 . 9 s) 2 + 9 . 5 rad = 6 . 977 rad . 006 (part 1 of 2) 10.0 points A dentists drill starts from rest. After 1 . 28 s ouseph (jao888) HW06 tsoi (92940) 2 of constant angular acceleration it turns at a rate of 20240 rev / min. Find the drills angular acceleration. Correct answer: 1655 . 88 rad / s 2 . Explanation: Let : t = 1 . 28 s and f = 20240 rev / min . Since = 0, = f t = f t = 20240 rev / min 1 . 28 s 2 rev 1 min 60 s = 1655 . 88 rad / s 2 . 007 (part 2 of 2) 10.0 points Throughout what angle does the drill rotate during this period? Correct answer: 1356 . 5 rad. Explanation: = t + 1 2 t 2 = 0 + 1 2 (1655 . 88 rad / s 2 ) (1 . 28 s) 2 = 1356 . 5 rad . 008 10.0 points An automobile moves at constant speed down one hill and up another hill along the smoothly curved surface as shown below. car Which of the following diagrams best rep resents the directions of the velocity and the acceleration of the automobile at the instant that it is at the lowest position as shown?...
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This note was uploaded on 07/09/2011 for the course PHY 302 taught by Professor Staff during the Summer '08 term at University of Texas at Austin.
 Summer '08
 Staff
 Physics

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