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Unformatted text preview: pampalone (tp8327) HW#9 swaminathan (10500) 1 This print-out should have 19 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A block sliding on a horizontal surface has an initial speed of 0.5 m/s. The block travels a distance of 1 m as it slows to a stop. What distance would the block have trav- eled if its initial speed had been 1 m/s? 1. more information is needed to answer the question 2. 4 m correct 3. 0.5 m 4. 1 m 5. 2 m 6. 3 m Explanation: W nc =- f k L = 0- 1 2 m v 2- m g L =- 1 2 m v 2 L = v 2 2 g So the distance is proportional to the square of the initial speed. 002 (part 1 of 3) 10.0 points Sally applies a horizontal force of 345 N with a rope to drag a wooden crate across a floor with a constant speed. The rope tied to the crate is pulled at an angle of 52 relative to the floor. The acceleration of gravity is 9 . 8 m / s 2 . m F 345 N 5 2 How much force is exerted by the rope on the crate? Correct answer: 560 . 373 N. Explanation: Given : F h = 345 N , and = 52 . The horizontal component of the force exerted by the rope is defined by cos = F h F so that F = F h cos = 345 N cos 52 = 560 . 373 N . 003 (part 2 of 3) 10.0 points What work is done by Sally if the crate is moved 37 . 4 m? Correct answer: 12903 J. Explanation: The motion is in the direction of the hori- zontal component, so the work Sally does is W = F h d = (345 N) (37 . 4 m) = 12903 J . 004 (part 3 of 3) 10.0 points What work is done by the floor through force of friction between the floor and the crate? Correct answer:- 12903 J. Explanation: pampalone (tp8327) HW#9 swaminathan (10500) 2 F m F F h Since there is no acceleration, all her work is done against friction, so the work done by the friction force is- W . 005 (part 1 of 5) 10.0 points A 12.4 kg crate is pulled up a rough incline with an initial speed of 1.4 m/s. The pulling force is 128.0 N parallel to the incline, which makes an angle of 13.3 with the horizontal. The coefficient of kinetic friction is 0.34 and the crate is pulled a distance of 7.2 m....
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- Spring '08