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Unformatted text preview: Version PREVIEW Exam 1 Practice chelikowsky (59005) 1 This printout should have 26 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. Kinematics2 v1 001 10.0 points The graph shows position as a function of time for two trains running on parallel tracks. At time t = 0 the position of both trains is 0 (at the origin). position time t B B A Which is true? 1. At time t B , both trains have the same velocity. 2. In the time interval from t = 0 to t = t B , train B covers more distance than train A. 3. Somewhere before time t B , both trains have the same acceleration. 4. Both trains speed up all the time. 5. Both trains have the same velocity at some time before t B . correct Explanation: The slope of the curve B is parallel to line A at some point t < t B . Calc Practice 03 002 10.0 points Suppose the position equation for a moving object is given by s ( t ) = 3 t 2 + 2 t + 5 where s is measured in meters and t is mea sured in seconds. Find the velocity of the object when t = 2. 1. 10 m/sec 2. 6 m/sec 3. 13 m/sec 4. 14 m/sec correct 5. None of these Explanation: s ( t ) = 3 t 2 + 2 t + 5 The velocity is v ( t ) = s ( t ) = 6 t + 2 and v (2) = 14. Dropped vs Thrown Balloons 003 10.0 points You and your friend throw balloons filled with water from the roof of a several story apart ment house. You simply drop a balloon from rest. A second balloon is thrown downward by your friend 4 s later with an initial speed of 78 . 4 m / s. They hit the ground simultane ously. How high is the apartment house? The acceleration of gravity is 9 . 8 m / s 2 . Neglect air resistance. 1. @@@ 2. @@@ 3. @@@ 4. @@@ 5. @@@ 6. @@@ 7. @@@ 8. @@@ 9. @@@ 10. @@@ Correct answer: 176 . 4 m. Explanation: Version PREVIEW Exam 1 Practice chelikowsky (59005) 2 t = 4 s , v = 78 . 4 m / s , and g = 9 . 8 m / s 2 . For balloon 1 y 1 = 1 2 g t 2 1 , and for balloon 2 y 2 = v t 2 + g t 2 2 2 . Balloon 2 is thrown t sec onds after balloon 1 and they hit the ground at the same time, so t 1 = t 2 + t and y 1 = y 2 g t 2 1 2 = v ( t 1 t ) + g 2 ( t 1 t ) 2 = v ( t 1 t ) + g 2 [ t 2 1 2 t 1 t + ( t ) 2 ] ( v g t ) t 1 = v t g 2 ( t ) 2 t 1 = v t g 2 ( t ) 2 v g t = (78 . 4 m / s)(4 s) 1 2 (9 . 8 m / s 2 )(4 s) 2 78 . 4 m / s (9 . 8 m / s 2 ) (4 s) = 6 s , so the height of the house is y = g t 2 1 2 = (9 . 8 m / s 2 ) (6 s) 2 2 = 176 . 4 m . Position vs Time 01 004 10.0 points An object was suspended in a fixed place ( y = 0) and then allowed to drop in a free fall. Taking up as the positive vertical direction, which of the following graphs correctly repre sents its vertical motion as displacement vs time ?...
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 Summer '08
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