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Unformatted text preview: Version 022/AABBC Test #1 Antoniewicz (56445) 1 This printout should have 20 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 9.0 points A rubber ball is dropped from rest onto the floor, and bounces back up to the same height from which it started. Ignore the force of fric tion due to the air. Which of the following sets of plots most accurately depict this mo tion? (The force plots depict the force on the ball by the environment.) 1. t y t v y t F y 2. t y t v y t F y 3. t y t v y t F y 4. t y t v y t F y correct 5. t y t v y t F y Explanation: Since there is a constant force, gravity, downward, the plot of the yposition should be parabolic with negative slope whose mag nitude is increasing over time, until it hits the floor. At this point the slope should switch sign and point upward and decrease in mag nitude over time. The velocity should be ini tially 0 m/s since the ball started from rest, and decrease linearly until it hits the floor, at which point it is very quickly given a boost to a positive value, and again continues to de crease linearly. The force should be always a negative constant value, except for when the ball hits the floor, at which point it should be a narrow positive peak to indicate the brief upward force exerted on the ball by the floor. 002 (part 1 of 3) 3.0 points A basketball player wishes to throw the ball to a teammate across the court. If he throws the ball at a 30 angle, with what initial speed must he throw the ball so that his teammate receives the ball in t flight = 0 . 69 s? Use g = 9 . 8 m / s 2 . 1. 14.994 2. 10.29 3. 6.762 4. 8.82 5. 9.408 6. 7.644 7. 14.7 8. 15.288 9. 15.582 10. 12.348 Correct answer: 6 . 762 m / s. Explanation: Using the momentum principle in the y direction, p f,y = p i,y + F net ,y t 0 = p i,y mg parenleftbigg t flight 2 parenrightbigg v i,y = g parenleftbigg t flight 2 parenrightbigg and since v i,y =  vectorv i  sin ,  vectorv i  = g t flight 2 sin = 6 . 762 m / s . Version 022/AABBC Test #1 Antoniewicz (56445) 2 003 (part 2 of 3) 3.0 points What is the highest point along the trajec tory, vectorr apex = ( r apex,x , r apex,y , ) , relative to the throwers hand ? (Take the initial loca tion to be the r i = ( , , ) m.) First give r apex ,x . 1. 6.11068 2. 6.73702 3. 6.42003 4. 13.2945 5. 2.02034 6. 5.51488 7. 3.91083 8. 4.94965 9. 3.43725 10. 9.93367 Correct answer: 2 . 02034 m. Explanation: The highest point occurs at t = t flight / 2. For the x coordinate, r apex ,x = v i,x t flight 2 = ( v i cos ) t flight 2 = 2 . 02034 m . 004 (part 3 of 3) 3.0 points Find r apex,y ....
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This note was uploaded on 09/14/2011 for the course PHY 56455 taught by Professor Antoniewicz during the Fall '11 term at University of Texas at Austin.
 Fall '11
 Antoniewicz

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