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Unformatted text preview: hernandez (ejh742) oldmidterm 03 Turner (58120) 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 rotating bicycle wheel has an angular speed of 40 / s at 3 . 6 s and a constant angular acceleration of 37 / s 2 . With the center of the wheel at the origin, the valve stem is on the positive xaxis (horizontal) at t = 1 . 3 s. Through what angle has the valve stem turned between 1 . 3 s and 7 . 1 s? Correct answer: 360 . 76 . Explanation: Let : 1 = 40 / s , t 1 = 3 . 6 s , = 37 / s 2 , = 0 , t = 1 . 3 s , and t = 7 . 1 s . The initial angular velocity can be deter mined from 1 = + ( t 1 t ) = 1 ( t 1 t ) = 40 / s (37 / s 2 ) (3 . 6 s 1 . 3 s) = 45 . 1 / s . This 2 = ( t 2 t ) + 1 2 ( t 2 t ) 2 = ( 45 . 1 / s) (7 . 1 s 1 . 3 s) + 1 2 (37 / s 2 ) (7 . 1 s 1 . 3 s) 2 = 360 . 76 . 002 (part 1 of 3) 10.0 points A beetle takes a joy ride on a pendulum. The string supporting the mass of the pendulum is 160 cm long. If the beetle rides through a swing of 37 , how far has he traveled along the path of the pendulum? Correct answer: 103 . 324 cm. Explanation: Let : r = 160 cm , and = 37 . Arc length is defined as s = r = (160 cm)(37 ) parenleftBig 180 parenrightBig = 103 . 324 cm . 003 (part 2 of 3) 10.0 points What is the displacement experienced by the beetle while moving theough the same angle 37 ? Correct answer: 101 . 538 cm. Explanation: Using the law of cosines, we have bardbl vector R bardbl = radicalbig r 2 + r 2 2 r r cos = r radicalbig 2 (1 cos ) = (160 cm) radicalbig 2(1 cos 37 ) = 101 . 538 cm . Alternative Solution: Divide the isosce les triangle in half. Then bardbl vector R bardbl = 2 . r sin parenleftbigg 2 parenrightbigg = 2 . 0 (160 cm) sin18 . 5 = 101 . 538 cm . 004 (part 3 of 3) 10.0 points If the pendulum at some instant is swinging at 2 . 5 rad / s, how fast is the beetle traveling? Correct answer: 400 cm / s. Explanation: hernandez (ejh742) oldmidterm 03 Turner (58120) 2 Let : = 2 . 5 rad / s . Linear and angular velocity are related by v = r = (160 cm)(2 . 5 rad / s) = 400 cm / s . keywords: 005 10.0 points At t = 0, a wheel rotating about a fixed axis at a constant angular deceleration of 0 . 56 rad / s 2 has an angular velocity of 2 . 5 rad / s and an angular position of 6 . 2 rad. What is the angular position of the wheel after 3 s? Correct answer: 11 . 18 rad. Explanation: Let : = . 56 rad / s 2 , = 2 . 5 rad / s , = 6 . 2 rad , and t = 3 s ....
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This note was uploaded on 06/14/2011 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner
 Physics

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