4.1.2.P24 (also 3.2.2.P10)
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The picture at the right shows a single frame from a video of a juggler tossing three balls up and down. In this frame, he has caught the central ball and is holding it so the ball is momentarily at rest. This corresponds to the time t = 0. In the video, he then throws the ball upwards it goes upward, it reaches its highest point a few moments later, and then it comes most of the way down to his hand, but the video stops before he catches it again. Taking position and time data, the video analysis program finds velocity and acceleration for the ball at each time. A smoothed version of the acceleration graph for the range of times described is shown below. (The full video can be watched by clicking on JugglerVideo.
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For each of the following physical descriptions of an instant of time, select the letters on the acceleration graph corresponds to those instants. Be sure to give all the instants that most likely match the physical description. If none match, put N.
1.1 At this instant, the ball is moving upward with its maximum speed.
1.2 At this instant, his hand releases the ball.
1.3 At this instant, the ball has velocity 0.
1.4 At this instant, the ball is traveling upward.
1.5 At this instant, the juggler is exerting no force on the ball.
For each answer, explain your reasoning.
Joe Redish 10/6/16
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