hw15 - lenoir (wml297) oldhomework 15 Turner (58220) 1 This...

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Unformatted text preview: lenoir (wml297) oldhomework 15 Turner (58220) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A box of mass m with an initial velocity of v slides down a plane, inclined at with respect to the horizontal. The coefficient of kinetic friction is . The box stops after sliding a distance x . m k v How far does the box slide? 1. x = v 2 2 g sin 2. x = v 2 2 g cos 3. x = v 2 2 g ( cos + sin ) 4. x = v 2 2 g (sin cos ) 5. x = v 2 2 g ( cos sin ) correct 6. x = v 2 g (sin cos ) 7. x = v 2 g ( sin + cos ) 8. x = v 2 2 g ( sin + cos ) 9. x = v 2 2 g ( sin cos ) 10. x = v 2 g ( sin 2 cos ) Explanation: The net force on the block parallel to the incline is F net = F mg sin F f , where F f is the friction force. Thus, Newtons equation for the block reads ma = mg sin F f = mg sin N = mg (sin cos ) a = g (sin cos ) , where N = mg cos . To find the distance the block slides down the incline, use v 2 = v 2 + 2 a ( x x ) , valid for a body moving with a constant accel- eration. Since x = 0 and v f = 0 (the block stops), we get x = v 2 2 a = v 2 2 g (sin cos ) = v 2 2 g ( cos sin ) . 002 (part 1 of 4) 10.0 points A particle of mass m moves along the x axis. Its position varies with time according to x = (6 m / s 3 ) t 3 (8 m / s 2 ) t 2 . What is the velocity of the particle at any time t ? 1. v = (6 m / s 2 ) t 2 (12 m / s) t 2. v = (6 m / s 2 ) t 2 (18 m / s) t 3. v = (12 m / s 2 ) t 2 (14 m / s) t 4. v = (9 m / s 2 ) t 2 (8 m / s) t 5. v = (12 m / s 2 ) t 2 (16 m / s) t 6. v = (24 m / s 2 ) t 2 (12 m / s) t 7. v = (18 m / s 2 ) t 2 (16 m / s) t correct 8. v = (21 m / s 2 ) t 2 (18 m / s) t 9. v = (6 m / s 2 ) t 2 (10 m / s) t lenoir (wml297) oldhomework 15 Turner (58220) 2 10. v = (6 m / s 2 ) t 2 (4 m / s) t Explanation: The velocity of the particle is v = dx dt = d dt bracketleftbig (6 m / s 3 ) t 3 (8 m / s 2 ) t 2 bracketrightbig = (18 m / s 2 ) t 2 (16 m / s) t . 003 (part 2 of 4) 10.0 points What is the acceleration of the particle at any time t ? 1. a = (12 m / s) t (16 m) 2. a = (24 m / s) t (18 m) 3. a = (36 m / s) t (6 m) 4. a = (42 m / s) t (8 m) 5. a = (42 m / s) t (16 m) 6. a = (54 m / s) t (14 m) 7. a = (36 m / s) t (16 m) correct 8. a = (48 m / s) t (12 m) 9. a = (12 m / s) t (18 m) 10. a = (54 m / s) t (10 m) Explanation: The acceleration of the particle is a = dv dt = d dt bracketleftbig (18 m / s 2 ) t 2 (16 m / s) t bracketrightbig = (36 m / s) t (16 m) ....
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This note was uploaded on 04/15/2010 for the course PHY 12343 taught by Professor Turner during the Spring '10 term at University of Texas at Austin.

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hw15 - lenoir (wml297) oldhomework 15 Turner (58220) 1 This...

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