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Unformatted text preview: Su (ycs73) – 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 (part 1 of 5) 10.0 points A child weighing 37 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 11 N and is tilted at an angle of 28 ◦ 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: 42 . 4698 N m. Explanation: τ C = M C g parenleftbigg l 2 parenrightbigg cos θ = 37 N 2 . 6 m 2 cos 28 ◦ = 42 . 4698 N m . 002 (part 2 of 5) 10.0 points What torque does the weight of the seesaw exert about the pivot point? Take counter clockwise to be positive. Correct answer: 0 N m. Explanation: This must be zero since the center of mass of the seesaw is just at the center, namely at the pivot. 003 (part 3 of 5) 10.0 points What torque does the rope exert about the pivot point? Take counterclockwise to be positive. Correct answer: 42 . 4698 N m. Explanation: Since the seesaw doesn’t rotate, the total torque should be zero. The torque which balances the torque of the child is from the rope. They have opposite directions but the same magnitude. 004 (part 4 of 5) 10.0 points What force does the rope exert downwards on the seesaw? Give a positive answer. Correct answer: 37 N....
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 Spring '09
 TSOI
 Force, Mass, Heat, Trigraph, Correct Answer

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