Phy 121
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: friction, gravity
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 will increase as the ball rises until the point where the ball briefly stops and the speed will be 0 at that point, then the ball will gain the same amount of speed until it again reaches 0 when the ball is caught
Describe the path of the ball as it would be observed by someone standing along the side of the road.
answer/question/discussion: the path of the ball will make an arc since the car is already moving
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 path probably would not differ if the bike was traveling at the same speed as the car, not catching the ball will increase the distance the ball falls
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 interval between the roof and the floor the ball starts with speed 0 and increases speed until it hit’s the floor, the acceleration of the ball will be 9.8m/s^2 since it is in the positive direction of gravity
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: with the car moving it will look like to the child that the ball falls in a diagonal direction since the car is moving, from the road the ball will look like it is falling straight down
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20min
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No need to revise, but do check the link:
&#At least part of your solution does not agree with the solution and comments given at the link below. You should view the solution at that link and self-critique as indicated there.
Solution
This link also expands on these topics and alerts you to many of the common errors made by students in the first part of this course. &#