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Phy 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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Copy the problem below into a text editor or word processor.
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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: ->->->->->->->->->->->-> :
Since car is moving, and its acceleration is constant, and we can ignore air resistance, the only force acting on the Ball between time of release and when it is caught, are those of 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 will have to overall match that of the horizontal constant velocity, in order for it to be caught. It is the same as throwing an object from a stationary position, if you are in a car moving at a constant horizontal velocity. As far as vertical speed vs. time interval, the ball’s velocity upward will gradually decrease until maximum point reach, and ball’s velocity downward will gradually increase in order to match that of horizontal constant velocity.
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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: ->->->->->->->->->->->-> :
Observed by someone standing along the side of the road, the path of the ball would simply be vertical in direction.
from the side of the road the ball's path will appear parabolic; from inside the car it will appear vertical
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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: ->->->->->->->->->->->-> :
The path of the ball would be different if the child was coasting along on a bicycle in a couple different ways. One, due to air resistance, the ball would travel backwards or horizontal in direction, unless it was thrown at a required forward angle. Additionally, again attributed towards air pressure, the ball would perhaps not obtain the same level of altitude. If the kid did not bother to catch the ball, the ball would continue decent at horizontally backwards and vertically downward.
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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 speed of the ball will change as there will be a vertical change of distance, as acceleration will be constant at 9.8 m/s^2. Therefore, the speed of the ball will increase constantly with distance traveled.
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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: ->->->->->->->->->->->-> :
I suppose the child would witness simply vertical motion of the ball, as it is stated that the ball is dense and the car is moving at a slow speed, in which air resistance may not be noticeable from the child’s positional viewpoint. However, from the observer’s perspective by the side of the road, he or she would perhaps notice slight horizontal movement of the ball along with of course vertical motion. Then again, maybe not, perhaps the observer would also only witness vertical motion of the ball, and I feel what would determine this would be the actual mass of the ball, and the velocity or speed of the moving vehicle.
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35-40 minutes
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10/21 3 pm
Copy the problem below into a text editor or word processor.
• This form accepts only text so a text editor such as Notepad is fine.
• You might prefer for your own reasons to use a word processor (for example the formatting features might help you organize your answer and explanations), but note that formatting will be lost when you submit your work through the form.
• If you use a word processor avoid using special characters or symbols, which would require more of your time to create and will not be represented correctly by the form.
• As you will see within the first few assignments, there is an easily-learned keyboard-based shorthand that doesn't look quite as pretty as word-processor symbols, but which gets the job done much more efficiently.
You should enter your answers using the text editor or word processor. You will then copy-and-paste it into the box below, and submit.
________________________________________
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: ->->->->->->->->->->->-> :
Horizontal velocity is constant at 10 m/s.
‘ds = 10 m/s * ½ s
= 5 meters
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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: ->->->->->->->->->->->-> :
I would say the path of the ball from its release until the instant it was caught, as observed by the passenger, would be that of the same regarding the child’s view, in that the ball travels at a straight upward motion, vertical movement.
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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: ->->->->->->->->->->->-> :
My sketch expresses that a line of people standing along the side of the road, would observe the path of the ball more as projectile, meaning that the ball would have horizontal motion to it as well with vertical motion.
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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: ->->->->->->->->->->->-> :
Vy = Vy0 – gt
0 m/s = Vy0 – (9.8 m/s^2)(1/2s)
Vy0 = 4.9 m/s
For the initial vertical velocity from the ground view, not sure if I used correct formula:
0 = 0 + Vy0(t) + ½ (a)(t^2)
Vy0 = 1.225 m / 0.5 s
= 2.5 m/s
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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: ->->->->->->->->->->->-> :
y = (4.9 m/s)^2 – (0 m/s)^2 / 2 * 9.8 m/s^2
y = 1.23 meters
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45 min.
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10/22 10 am
You got most but did miss a few, and on those should submit revisions.
&#See any notes I might have inserted into your document, and before looking at the link below see if you can modify your solutions. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your old and new 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.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#
&#See any notes I might have inserted into your document, and before looking at the link below see if you can modify your solutions. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your old and new 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.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#