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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.
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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):
The answer is 6. Divide Length (30 cm) by the time (5 sec).
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Your number and your overall procedure are correct.
However the result has units, which are also essential:
30 cm / (5 s) = 6 cm / s.
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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):
Its final velocity is 12. Multiply 6 times 2, because its average velocity is at the half-way point.
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By how much did its velocity therefore change?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
12-6 is 6 so it changed by 6 .
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The final velocity 12 cm / s but the velocity is not initially 6 cm/s. 6 cm/s is the average velocity, which is not directly related to the change in velocity.
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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):
It was an average rate of 2.4 seconds. Divide the final velocity of 12 by 5 seconds.
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This is a good calculation, but the units aren't right.
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Twenty Minutes
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