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Unformatted text preview: This printout should have 12 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points Find the magnitude of the torque produced by a 4.8 N force applied to a door at a per pendicular distance of 0.21 m from the hinge. Correct answer: 1 . 008 N m. Explanation: Let : F = 4 . 8 N , d = 0 . 21 m , and = 90 . . = F d sin = (4 . 8 N) (0 . 21 m) sin 90 . = 1 . 008 N m . 002 10.0 points An Atwood machine is constructed using a disk of mass 2 . 3 kg and radius 23 . 7 cm. 3 . 7 m 23 . 7 cm 2 . 3 kg 1 . 78 kg 1 . 12 kg What is the acceleration of the system? The acceleration of gravity is 9 . 8 m / s 2 . Correct answer: 1 . 59704 m / s 2 . Explanation: Let : m = 2 . 3 kg , R = 23 . 7 cm = 0 . 237 m , m 1 = 1 . 12 kg , m 2 = 1 . 78 kg , and h = 3 . 7 m . Consider the free body diagrams 1 . 78 kg 1 . 12 kg T 2 T 1 m 2 g m 1 g a a The net acceleration a = r is in the di rection of the heavier mass m 1 . For the mass m 1 , F net = m 1 a = m 1 g T 1 T 1 = m 1 g m 1 a and for the mass m 2 , F net = m 2 a = T 2 m 2 g T 2 = m 2 a + m 2 g . The pulley is a solid disk, so I = 1 2 mr 2 and net = ccw cw = I T 1 r T 2 r = 1 2 mr 2 a r = 1 2 mr a Multiplying by 2 r gives ma = 2 T 1 2 T 2 = 2 ( m 1 m 2 ) g 2 ( m 1 + m 2 ) a a = 2 ( m 1 m 2 ) g m + 2 m 1 + 2 m 2 = 2 (1 . 12 kg 1 . 78 kg) (9 . 8 m / s 2 ) 2 . 3 kg + 2 (1 . 12 kg) + 2 (1 . 78 kg) = 1 . 59704 m / s 2 . 003 10.0 points A 308 kg merrygoround in the shape of a horizontal disk with a radius of 1 . 3 m is set in motion by wrapping a rope about the rim of the disk and pulling on the rope....
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This note was uploaded on 10/03/2010 for the course PH 101 taught by Professor Jones,s during the Spring '08 term at Alabama.
 Spring '08
 Jones,S
 Physics, Force

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