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Unformatted text preview: alexander (jra2623) homework 09 Turner (92510) 1 This printout should have 13 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 light, inextensible cord passes over a light, frictionless pulley with a radius of 5 . 4 cm. It has a(n) 16 kg mass on the left and a(n) 3 . 6 kg mass on the right, both hanging freely. Initially their center of masses are a vertical distance 1 . 7 m apart. The acceleration of gravity is 9 . 8 m / s 2 . 1 . 7 m 5 . 4 cm 16 kg 3 . 6 kg At what rate are the two masses accelerat ing when they pass each other? Correct answer: 6 . 2 m / s 2 . Explanation: Let : R = 5 . 4 cm , m 1 = 3 . 6 kg , m 2 = 16 kg , h = 1 . 7 m , and v = R . Consider the free body diagrams 16 kg 3 . 6 kg T T m 2 g m 1 g a a Since the larger mass will move down and the smaller mass up, we can take motion downward as positive for m 2 and motion up ward as positive for m 1 . Apply Newtons second law to m 1 and m 2 respectively and then combine the results: For mass 1: summationdisplay F 1 : T m 1 g = m 1 a (1) For mass 2: summationdisplay F 2 : m 2 g T = m 2 a (2) We can add Eqs. (1) and (2) above and obtain: m 2 g m 1 g = m 1 a + m 2 a a = m 2 m 1 m 1 + m 2 g = 16 kg 3 . 6 kg 16 kg + 3 . 6 kg (9 . 8 m / s 2 ) = 6 . 2 m / s 2 . 002 (part 2 of 2) 10.0 points What is the tension in the cord when they pass each other? Correct answer: 57 . 6 N. Explanation: T = m 1 ( g + a ) = (3 . 6 kg) (9 . 8 m / s 2 + 6 . 2 m / s 2 ) = 57 . 6 N ....
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This note was uploaded on 10/20/2011 for the course PHY 302K taught by Professor Kaplunovsky during the Summer '08 term at University of Texas at Austin.
 Summer '08
 Kaplunovsky
 Friction, Mass, Light

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