exam_1_practice

# exam_1_practice - Version PREVIEW – Exam 1 Practice –...

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Unformatted text preview: Version PREVIEW – Exam 1 Practice – chelikowsky – (59005) 1 This print-out should have 26 questions. Multiple-choice 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 Δ 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 Δ t sec- onds after balloon 1 and they hit the ground at the same time, so t 1 = t 2 + Δ t and y 1 = y 2 g t 2 1 2 = v ( t 1 − Δ t ) + g 2 ( t 1 − Δ t ) 2 = v ( t 1 − Δ t ) + g 2 [ t 2 1 − 2 t 1 Δ t + (Δ t ) 2 ] ( v − g Δ t ) t 1 = v Δ t − g 2 (Δ t ) 2 t 1 = v Δ t − g 2 (Δ t ) 2 v − g Δ 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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exam_1_practice - Version PREVIEW – Exam 1 Practice –...

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