Phys 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.
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, Potentital energy when it reaches it's peak and when child releases the ball, kenetic energy.
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 slows down going up and as it comes back down it picks up speed due to gravity. On a graph og speed vs. clock time, the graph would show a decrease in velocity as the time increased until it got to its peak, then the slope will increasing velocity at a decreasing time interval on the way down.
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 would apear to go in the same path as it did coming down.
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 woul d go in a parabola type motion, like a projectile. If the boy did not catch the ball, it would land infront of him.
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 speed of the ball falling to the floor will be a constant 9.8m/s^2 in the downward direction.
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 motion of the ball by the child will appear to be suspended in mid air for a second because the ball will traveling at the same speed the car is, but then will quickly drop to the ground. To the observer from the outside, the ball will look to be dropping in a straight line due to gravity.
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10 min
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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:
The ball traveled 5m. ds=v*dt
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:
The ball apeared to be going in the negative direction since the car was moving forward and the child was staying still.
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 shape of the path of the ball is a positive parabola.
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:
How high did the ball rise above its point of release before it began to fall back down?
answer/question/discussion:
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10 min
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Time is short and you might not have time to compare with the discussions at the links below. Do so if you can, and if you have questions let me know.
&#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. &#
&#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. &#