Phy231
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.
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: ->->->->->->->->->->->-> :
gravitational force, the force of the car moving, the force of the boy tossing the ball
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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 at first will be the greatest because of the force of being tossed, it will start to slow down due to gravity pushing
against it, eventually gravity will overcome the initial force of the toss and the ball will stop accelerating. Then the ball will
change direction and start to come down and once again the acceleration will increase until the child catches the ball. Then
the ball will come to rest 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: ->->->->->->->->->->->-> :
The ball will go up but with the movment of the car, so it would be going up towards the left. The ball would then start to
fall also going left, so it would look like a line climbing right to left, meeting a peak, and then falling right to left.
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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: ->->->->->->->->->->->-> :
No, the ball would continue to fall at right to left incline, but if the child doens't catch it then they'll pass wherever the
ball hits the ground. It's acceleration will also increase.
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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 acceleration will increase until the ball hits the ground. The ball should have an acceleration of 9.8m/s^2 because
that is the force of gravity.
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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 appear to falling towards the back of the car because the motion of the car isn't going to have an effect on the
ball now that it is outside the car. An observer would see the very same thing as the child.
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20min
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5/14/10 2pm
A child in a car tosses a ball upward so that after release it requires 1/2 second to rise and fall back into the child's
hand at the same height from which it was released. The car is traveling at a constant speed of 10 meters / second in the
horizontal direction.
Between release and catch, how far did the ball travel in the horizontal direction?
answer/question/discussion: ->->->->->->->->->->->-> :
h_'ds=10m/s*.5s=5m
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As observed by a passenger in the car, what was the path of the ball from its release until the instant it was caught?
answer/question/discussion: ->->->->->->->->->->->-> :
straight up and down
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Sketch the path of the ball as observed by a line of people standing along the side of the road. Describe your sketch.
What was shape of the path of the ball?
answer/question/discussion: ->->->->->->->->->->->-> :
The graph would be a straight line up and down. The observers would see the ball go up and come down, not paying attention
to the movement of the car.
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How fast was the ball moving in the vertical direction at the instant of release? At that instant, what is its velocity as
observed by a line of people standing along the side of the road?
answer/question/discussion: ->->->->->->->->->->->-> :
It depends on the force of child on the ball, the people along the road would see something similar to the child.
vf=0m/s 'dt=.25s Am I missing some other piece of information.
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How high did the ball rise above its point of release before it began to fall back down?
answer/question/discussion: ->->->->->->->->->->->-> :
Once again I think I'm missing some piece of information.
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20min
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5/14/10 2pm
&#Please compare your solutions with the expanded discussion at the link
Solution
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&#Please compare your solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified. &#