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Phy 121
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.
** CQ_1_03.1_labelMessages.txt **
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):
30cm/5s = 6cm/s = vAve
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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):
(0cm/s + x) / 2 = 30cm/s
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(0cm/s + x) / 2 would be the average velocity of a uniformly accelerating object with initial velocity of 0 and final velocity x.
However the average velocity of this object isn't 30 cm/s. Its displacement is 30 cm, but you previously calculated the correct average velocity, which is 6 cm/s.
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0cm/s + x = 60cm/s
X = 60cm/s = Vf
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• By how much did its velocity therefore change?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The velocity changed 60cm/s
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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):
60cm/s - 0cm/s / 5s = 12cm/s/s
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If that 60 cm/s velocity was in fact the final velocity, this would be correct.
You should find it easy to revise this by first calculating the correct final velocity. Except for that one error, your reasoning is good throughout.
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