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Unformatted text preview: kim (jkk547) – HW08 – Tsoi – (58020) 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 Two weights attached to a uniform beam of mass 56 kg are supported in a horizontal po sition by a pin and cable as shown in the figure. The acceleration of gravity is 9 . 8 m / s 2 . 22 kg 59 kg 2 . 6 m 8 . 4 m 45 ◦ 56 kg What is the tension in the cable which sup ports the beam? Correct answer: 1 . 30013 kN. Explanation: Let : m = 56 kg , M 1 = 22 kg , M 2 = 59 kg , L 1 = 2 . 6 m , L 2 = 8 . 4 m , and θ = 45 ◦ . Basic Concepts: summationdisplay vector F = 0 summationdisplay vector τ = 0 . Solution: The sum of the torques about the pivot is T L 2 sin θ mg L 2 2 M 1 gL 1 M 2 gL 2 = 0 Solving for the tension T T = mg L 2 2 + M 1 g L 1 + M 2 g L 2 L 2 sin θ = (56 kg)(9 . 8 m / s 2 ) parenleftbigg 8 . 4 m 2 parenrightbigg (8 . 4 m) sin θ + (22 kg)(9 . 8 m / s 2 )(2 . 6 m) (8 . 4 m) sin θ + (59 kg)(9 . 8 m / s 2 )(8 . 4 m) (8 . 4 m) sin θ = 1 . 30013 kN . 002 (part 1 of 5) 10.0 points A child weighing 38 N climbs onto the right end of a seesaw, little knowing that it is tied down with a rope at its left end. The seesaw is 2 . 6 m long, weighs 12 N and is tilted at an angle of 17 ◦ from the horizontal. The center of mass of the seesaw is half way along its length, and lies right above the pivot. l θ What torque does the weight of the child exert about the pivot point? Take counter clockwise to be positive. Correct answer: 47 . 2415 N m....
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This note was uploaded on 10/04/2009 for the course PHY 58020 taught by Professor Tsoi during the Fall '09 term at University of Texas.
 Fall '09
 TSOI
 Physics

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