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Phy 121
Your 'cq_1_09.1' 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 accelerates uniformly as it rolls 20 cm down a ramp, starting from rest, in 2 seconds.
• What are its average velocity, final velocity and acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
vAve = ‘ds/’dt = 20 cm/2 sec = 10 cm/sec
vAve = (v0 + vf)/2
10 cm/sec = (0 cm/sec + vf)/2
20 cm/sec = vf
Acceleration is (20 cm/sec – 0 cm/sec)/2 sec
Acceleration = 10 cm/s^2
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• If the time interval is in error so that it is 3% longer than the actual time interval, then what are the actual values of the final velocity and acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
So the actual time is 2.06 seconds
vAve = ‘ds/’dt = 20 cm/2.06 sec = 9.7 cm/sec
vAve = (v0 + vf)/2
9.7 cm/sec = (0 cm/sec + vf)/2
19.4 cm/sec = vf
Acceleration is (19.4 cm/sec – 0 cm/sec)/2 sec
the denominator should be 3% longer than 2 sec
Acceleration = 9.7 cm/s^2
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• What is the percent error in each?
answer/question/discussion: ->->->->->->->->->->->-> :
velocity: 0.1/9.7 cm/s * 100% = 1%
acceleration: 0.1/9.7 cm/s^2 * 100% = 1%
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• If the percent error is the same for both velocity and acceleration, explain why this must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
The error is in the seconds, which effects both velocity and acceleration in the same way.
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• If the percent errors are different explain why it must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
N/A
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Solution
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