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Phy 231
Your 'cq_1_07.1' 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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Copy the problem below into a text editor or word processor.
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A ball falls freely from rest at a height of 2 meters. Observations indicate that the ball reaches the ground in .64 seconds.
• Based on this information what is its acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
ds/dt= vAve 2m/.64s= 3.125m/s
vf= 3.125m/s * 2 – 0m/s= 6.25m/s
aAve= (6.25m/s – 0m/s)/.64s= 9.77m/s^2
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• Is this consistent with an observation which concludes that a ball dropped from a height of 5 meters reaches the ground in 1.05 seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
ds/dt= 5m/1.05s= 4.76m/s=vAve
4.76m/s * 2 – 0= 9.52m/s= vf
aAve= (9.52m/s – 0m/s)/1.05s= 9.07m/s^2
No its not consistent because a is not the same in both problems.
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@& You judgement of consistency would depend on the accuracy of the timing. A 5% uncertainty in timing would result in a 10% uncertainty in calculated acceleration and could easily explain the discrepancy, in which case your results would not be considered inconsistent. If the timing was done using the TIMER program the uncertainty would be much greater, and the two results would be consistent to within the limits of the experiment.
If on the other hand the timing was done by more accurate means, the two results could certainly be regarded as inconsistent.*@
• Are these observations consistent with the accepted value of the acceleration of gravity, which is 9.8 m / s^2?
answer/question/discussion: ->->->->->->->->->->->-> :
The 1st observation is acceptable because it is only off by about .03m/s^2. The 2nd is not because it is off by about .73m/s^2. I suppose that if you wanted just a rough estimate then either would be acceptable.
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@& Again the judgement would depend on the degree of uncertainty in measurement. With very accurate measurements both results would be considered inconsistent. With less accurate measurements both might be considered consistent.*@
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&#Good responses. See my notes and let me know if you have questions. &#