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Unformatted text preview: hernandez (ejh742) oldhomework 28 Turner (58120) 1 This printout should have 11 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points The angle of the inclination is 38 . 5 , the outer part of the large pulley has a radius of 3 r and the inner part of the large pulley has a radius of r . 3 r r /2 r m T Find the mass m needed to balance the 1110 kg truck on the incline. The acceleration of gravity is 9 . 8 m / s 2 . Assume all pulleys are frictionless and massless and the cords are massless. Correct answer: 115 . 165 kg. Explanation: Let : = 38 . 5 , R = 3 r , and M = 1110 kg . Let T be the tension in the string around the inner part (radius = r ) of the pulley. Then from the force equilibrium for the small pulley at the truck 2 T M g sin = 0 T = 1 2 M g sin = 1 2 (1110 kg) ( 9 . 8 m / s 2 ) sin 38 . 5 = 3385 . 86 N . From rotational equilibrium of the large pul ley, summationdisplay = 0 mg (3 r ) T r = 0 m = T 3 g = 1 6 M sin = 1 6 (1110 kg) sin 38 . 5 = 115 . 165 kg . 002 10.0 points A massless beam supports two weights as shown. 680 N W L 4 L 4 L 2 L A B Find W such that the supporting force at A is zero. Correct answer: 340 N. Explanation: Let : W 1 = 680 N and F A = 0 . summationdisplay = 0, so for a fulcrum at B, W 1 L 4 = W L 2 W = 1 2 W 1 = 1 2 (680 N) = 340 N ....
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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, Work

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