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Unformatted text preview: Patel (pnp223) homework 09 Turner (92160) 1 This printout should have 10 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 12 cm. It has a(n) 21 kg mass on the left and a(n) 4 kg mass on the right, both hanging freely. Initially their center of masses are a vertical distance 4 . 8 m apart. The acceleration of gravity is 9 . 8 m / s 2 . 4 . 8 m 12 cm 21 kg 4 kg At what rate are the two masses accelerat ing when they pass each other? Correct answer: 6 . 664 m / s 2 . Explanation: Let : R = 12 cm , m 1 = 4 kg , m 2 = 21 kg , h = 4 . 8 m , and v = R . Consider the free body diagrams 21 kg 4 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 = 21 kg 4 kg 21 kg + 4 kg (9 . 8 m / s 2 ) = 6 . 664 m / s 2 . 002 (part 2 of 2) 10.0 points What is the tension in the cord when they pass each other?...
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 Spring '09
 Turner
 Physics, Work, Light

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