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phys 201
Your 'cq_1_03.1' 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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The problem:
A ball starts with velocity 0 and accelerates uniformly down a ramp of length 30 cm, covering the distance in 5 seconds.
• What is its average velocity?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Average acceleration = (vf - vi) / time
Vf = 30 / 5 = 6 cm/s
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You need to use units with every quantity that has units.
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That would include the numerator and denominator of your calculation.
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Your final result does have the correct units, but it's not the correct final velocity. Your calculation gives you an important quantity but it's not final velocity.
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Average acceleration = (6-0) / 5 = 1.2 cm/s
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You need to use units with every quantity that has units.
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Your final result does not have the units that follow from your calculation, nor does it have the units of the quantity you are trying to find.
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• If the acceleration of the ball is uniform then its average velocity is equal to the average of its initial and final velocities.
You know its average velocity, and you know the initial velocity is zero.
What therefore must be the final velocity?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
initial velocity = 0
final velocity = 6 cm/s
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This is not the correct final velocity (see my previous notes).
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• By how much did its velocity therefore change?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
change in velocity = average acceleration * time =
1.2 cm/s * 5 = 6 cm/s
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Most of the quantities used in your calculation don't have the correct units.
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• At what average rate did its velocity change with respect to clock time?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
(6 cm/s) / 5 s = 1.2 cm/s
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This isn't correct, but you do have the correct units on the left-hand side.
The units on the right-hand side don't follow from the units on the left-hand side.
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• What would a graph of its velocity vs. clock time look like? Give the best description you can.
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The graph of velocity versus clock time would be a positive straight line. The acceleration is increasing at a constant rate.
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The acceleration is not changing.
A straight-line velocity vs. clock time graph (which is indeed the case here) indicates an unchanging acceleration.
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*#&!*#&!
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You're on the right track but you're missing some important details, most of which you should be able to work out based on my notes
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
If my notes indicate that revision is optional, use your own judgement as to whether a revision will benefit you.
Spend a reasonable amount of time on your revision, but don't let yourself get too bogged down. After a reasonable amount of time, if you don't have at least a reasonable attempt at a solution, insert the best questions you can showing me what you do and do not understand, and I'll attempt to clarify further. &#
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