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phy 201
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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.
• 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: ->->->->->->->->->->->-> :
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 speed of the ball between the release and catch should increase
The graph of a speed vs. clock should be positively linear
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@& If the speed of the rising ball was increasing, then it would never come to rest and fall back down; there would be no limit to how high it would rise.*@
• Describe the path of the ball as it would be observed by someone standing along the side of the road.
answer/question/discussion: ->->->->->->->->->->->-> :
the ball will go up and down. Since the car is moving the ball will appear to be moving in a U shape
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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: ->->->->->->->->->->->-> :
Shouldn’t change if the boy is on a bicycle. But if the kid didn’t bother to catch the ball the ball would falling would travel more distance. Possibly increasing speed because it had more time to reach another force
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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: ->->->->->->->->->->->-> :
from the roof and floor will increase speed. The acceleration will remain the same. Because more time is give before a force stops 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 ball will drop quickly to the ground. It will be a vertical drop
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@& That would be the case from the child's perspective.
However an observer on the side of the road would observe the forward motion of the ball to continue, without slowing much.
What would the path of the ball ltherefore ook like according to the observer?*@
*#&!*#&!
@& Not bad, but you need to give a couple of these questions a little more thought. Don't spend a lot of time on it, but give it up to 15 minutes.
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