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Unformatted text preview: adamkiewicz (ja28724) Energy of a system Morozova (11102) 1 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 This question is typical on some drivers li cense exams: A car moving at 43 km / h skids 13 m with locked brakes. How far will the car skid with locked brakes at 107 . 5 km / h? Correct answer: 81 . 25 m. Explanation: 107 . 5 km / h 43 km / h = 2 . 5 At 2 . 5 times the speed, it has 6 . 25 times the KE parenleftbigg 1 2 m v 2 parenrightbigg and will skid 6 . 25 times as far: 81 . 25 m. Since the frictional force is about the same in both cases, the distance has to be 6 . 25 times as great for 6 . 25 times as much work done by the pavement on the car. 002 10.0 points The Joule and the kilowatthour are both units of energy. 11 . 9 kW h is equivalent to how many Joules? Correct answer: 4 . 284 10 7 J. Explanation: 1 W = 1 J / s 11 . 9 kW h = (11 . 9 kW h) 1000 W kW 3600 s 1 h = 4 . 284 10 7 W s = 4 . 284 10 7 J . 003 (part 1 of 5) 10.0 points A 18 . 9 kg block is dragged over a rough, hor izontal surface by a constant force of 118 N acting at an angle of angle 31 above the hor izontal. The block is displaced 48 . 2 m, and the coefficient of kinetic friction is 0 . 203....
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This note was uploaded on 04/14/2009 for the course PHYS 111 taught by Professor Moro during the Spring '08 term at NJIT.
 Spring '08
 moro
 Physics, Energy

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