cq_1_091

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PHY 241

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: ->->->->->->->->->->->-> :

Final Velocity= 20 cm/2s= 10cm/s

Average Velocity= 10cm/s+0cm/s/2= 5cm/s

Acceleration= 10cm/s/2s= 5cm/s^2

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@& Average velocity = `ds / `dt (by definition), so ave vel is 10 cm/s, not 5 cm/s.

You calculated ave vel in your first line but misidentified it*@

• 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: ->->->->->->->->->->->-> :

The new time is 2.06s

Final velocity= 20cm/2.06s= 9.71cm/s

Acceleration= 9.71cm/s/2.06s= 4.71cm/s^2

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• What is the percent error in each?

answer/question/discussion: ->->->->->->->->->->->-> :

10-9.71= 0.29/10*100= 2.9% error in Final velocity

5-4.71=.29/5*100= 5.8% error in acceleration

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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: ->->->->->->->->->->->-> :

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• If the percent errors are different explain why it must be so.

answer/question/discussion: ->->->->->->->->->->->-> :

The percent error is different because each quantity is measuring different quantities of the ball’s movement and the units are used differently.

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@& Your percent errors are correct.

You did make a systematic mistake in calculating the accelerations, but it affected all your results to the percent error is still correct in each case.

Be sure to see my note about identifying your quantities.*@

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