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Unformatted text preview: khounvivongsy (sk27799) Homework 5 Weathers (17104) 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 2) 10.0 points A particle has vectorr (0) = (4 m) and vectorv (0) = (2 m / s) . If its acceleration is constant and given by vectora = (2 m / s 2 ) ( + ), at what time t does the particle first cross the x axis? Correct answer: 2 s. Explanation: vectorr ( t ) = vectorr (0) + vectorv (0) t + 1 2 vectora t 2 , so vectorr ( t ) = (4 m) + (2 m / s) t +( 1 m / s 2 ) ( + ) t 2 = [(2 m / s) t (1 m / s 2 ) t 2 ] +[4 m (1 m / s 2 ) t 2 ] vectorr ( t ) will not have a y component when 4 m (1 m / s 2 ) t 2 = 0 (1 m / s 2 ) t 2 = 4 m t = 2 s . 002 (part 2 of 2) 10.0 points At what time t is the particle moving parallel to the y axis; that is, in the direction? Correct answer: 1 s. Explanation: vectorr ( t ) = vectorr (0) + vectorv (0) t + 1 2 vectora t 2 vectorv ( t ) = dvectorr d t = vectorv (0) + vectora t , so vectorv ( t ) = (2 m / s) (2 m / s 2 ) ( + ) t = [(2 m / s) (2 m / s 2 ) t ] (2 m / s 2 ) t vectorv ( t ) will not have an x component when 2 m / s (2 m / s 2 ) t = 0 t = 1 s . At this time vectorv ( t ) = (2 m / s) parallel to the yaxis. 003 10.0 points A home run is hit such a way that the baseball just clears a wall 30 m high located 123 m from home plate. The ball is hit at an angle of 36 to the horizontal, and air resistance is negligible. Assume the ball is hit at a height of 2 m above the ground.of 2 m above the ground....
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 Spring '09
 weathers
 Physics

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