Phy 201
Your 'cq_1_18.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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A child in a slowly moving car tosses a ball upward. It rises to a point below the roof of the car and falls back down, at which point the child catches it. During this time the car neither speeds up nor slows down, and does not change direction.
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What force(s) act on the ball between the instant of its release and the instant at which it is caught? You can ignore air resistance.
answer/question/discussion: upward force used in throwing the ball, downward force of gravity
The upward force ended when the ball was released, and does not act on the ball after released. The only force that ask after release, other than air resistance (which is neglected), is gravity.
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What happens to the speed of the ball between release and catch? Describe in some detail; a graph of speed vs. clock time would also be appropriate.
answer/question/discussion: the ball's initial velocity decreases as it leaves the boy's hand until it reaches the max height, at which time it will fall back down with its velocity increasing until it is caught again.
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Describe the path of the ball as it would be observed by someone standing along the side of the road.
answer/question/discussion: someone standing on the side of the road would see the ball's trajectory as a parabola.
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How would the path differ if the child was coasting along on a bicycle? What if the kid didn't bother to catch the ball? (You know nothing about what happens after the ball makes contact with the ground, so there's no point in addressing anything that might happen after that point).
answer/question/discussion: the child on the bike would see the ball's path the same way the child in the car sees it, straight up, straight down.
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What if the child drops the ball from the (inside) roof of the car to the floor? For the interval between roof and floor, how will the speed of the ball change? What will be the acceleration of the ball? (You know nothing about what happens after the ball makes contact with the floor, so there's no point in addressing anything that might happen after that point).
answer/question/discussion: the ball's speed will be the same. the acceleration in both cases would be the force of gravity pulling down on the ball.
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What if the child holds the ball out of an open window and drops it. If the ball is dense (e.g., a steel ball) and the car isn't moving very fast, air resistance will have little effect. Describe the motion of the ball as seen by the child. Describe the motion of the ball as seen by an observer by the side of the road. (You know nothing about what happens after the ball makes contact with the ground, so there's no point in addressing anything that might happen after that point).
answer/question/discussion: the child in the car would see the ball fall downward and back. Someone on the side of the road would see the ball fall straight down.
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15 minutes
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&#Good responses. Let me know if you have questions. &#