Phy 231
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 acts downwards on the ball, and no other forces after it leaves the child's hand.
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: From the moment of release the ball begins to experience the force of gravity and will have negative acceleration is up is positive, which is cause it to slow down until it reaches the peak of its motion, and then it will begin to fall back down gaining velocity until it is caught by the child. In a graph of velocity vs. clock time we would have a certain initial value that would decrease over time until it reach 0, and then continue below the x-axis at the clock time it reaches the apex of the toss, and continues to become increasingly negative in velocity.
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 be rising upwards it would have no motion in relation to the vehicle and would appear to be moving in the opposite direction of the vehicle during its motion inside.
The direction wouldn't be opposite.
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: If the child was coasting along on a bicycle he would have to provide horizontal velocity equal in magnitude and direction in order to catch it, because if he did not the ball would ideally have no horizontal motion while the child would; therefore, the child would have been unable to catch the ball without the horizontal motion and it would fall to the ground at a position directly below where the child released the ball.
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 velocity of the ball would increase with the acceleration of gravity, which is 9.8 m/s^2, and would continue to increase with respect to clock time until it reached the floor where for the purpose of this problem motion would cease.
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: From the child's perspective the ball is moving away from him/her diagonally with a combined vertical acceleration of gravity and the apparent horizontal acceleration from the motion of the vehicle away from the ball. From an observer by the side of the road, the ball would be seen as dropping straight down with no motion horizontally.
The child would see the ball drop straight down.
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25 minutes
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No need to submit anything more but be sure you see the explanations given at the link below.
&#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. &#
Phy 231
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.
** **
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 acts downwards on the ball, and no other forces after it leaves the child's hand.
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: From the moment of release the ball begins to experience the force of gravity and will have negative acceleration is up is positive, which is cause it to slow down until it reaches the peak of its motion, and then it will begin to fall back down gaining velocity until it is caught by the child. In a graph of velocity vs. clock time we would have a certain initial value that would decrease over time until it reach 0, and then continue below the x-axis at the clock time it reaches the apex of the toss, and continues to become increasingly negative in velocity.
Correct, but note that the question asked about speed rather than velocity.
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 be rising upwards it would have no motion in relation to the vehicle and would appear to be moving in the opposite direction of the vehicle during its motion inside.
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: If the child was coasting along on a bicycle he would have to provide horizontal velocity equal in magnitude and direction in order to catch it, because if he did not the ball would ideally have no horizontal motion while the child would; therefore, the child would have been unable to catch the ball without the horizontal motion and it would fall to the ground at a position directly below where the child released the ball.
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 velocity of the ball would increase with the acceleration of gravity, which is 9.8 m/s^2, and would continue to increase with respect to clock time until it reached the floor where for the purpose of this problem motion would cease.
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: From the child's perspective the ball is moving away from him/her diagonally with a combined vertical acceleration of gravity and the apparent horizontal acceleration from the motion of the vehicle away from the ball. From an observer by the side of the road, the ball would be seen as dropping straight down with no motion horizontally.
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25 minutes
** **
No need to submit anything more but be sure you see the explanations given at the link below.
&#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. &#