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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: ->->->->->->->->->->->-> n:
v0 = 0m/sec
`dt = 2sec
`ds = 20cm
If initial velocity is 0m/sec and total displacement is 20cm over 2 seconds we would need an average velocity of 10cm/sec. This means that vf must equal 20cm/sec. This also means that a 20cm/sec change in velocity over a 2sec time interval means average acceleration must be 10cm/sec^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: ->->->->->->->->->->->-> n:
`dt = 2.06sec
20cm = (0cm/sec + vf)/2 * 2.06sec
9.708737864cm/sec = vf/2
Vf = 19.42cm/sec
aAve = (19.42cm/sec-0cm/sec0/2.06sec = 9.43cm/sec^2
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What is the percent error in each?
answer/question/discussion: ->->->->->->->->->->->-> n:
For vF the percentage error is 3%
For aAve it is 6%
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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: ->->->->->->->->->->->-> n:
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If the percent errors are different explain why it must be so.
answer/question/discussion: ->->->->->->->->->->->-> n:
Our calculation for vF only uses one value that is in error by 3% making it’s percentage error also equal to 3%
aAve uses two calculations based on a 3% error making it’s percentage error equal to 6%
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&#Very good responses. Let me know if you have questions. &#