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PHY 121
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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):
30cm/5sec = 6cm/sec
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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):
6cm/sec
@& If the initial velocity is 0 and the final velocity is 6 cm/s, then the average velocity is 3 cm/s.
However you have already calculated the average velocity, which is 6 cm/s.
So your conclusion that the final velocity is 6 cm/s must be in error.
What must be the final velocity in order to have initial velocity 0 and average velocity 6 cm/s?*@
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By how much did its velocity therefore change?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Zero.
@& The velocity started out at zero. If the velocity hand't changed it wouldn't have gone anywhere.*@
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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):
There was no change??
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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):
Straight line that increases at a constant rate.
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*#&!
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