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.

** CQ_1_09.1_labelMessages **

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

vf=?

v0=0

'dt=2

`ds=20cm

a=?

vave= `ds/`dt

vave= 20cm/2s=10cm/s

vave=vf+vo/2

10cm/s=vf+0/2

Vf=20cm/s

20cm/s = 0 + a * 2

A=10cm/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: ->->->->->->->->->->->-> :

2s-3%=1.94s

vave= `ds/`dt

vave= 20cm/1.94s=10.31cm/s

vave=vf+vo/2

10.31cm/s=vf+0/2

Vf=20.62cm/s

20cm/s = 0 + a * 1.94

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The 3% error in the time has already changed the final velocity. You wouldn't apply the final velocity from the earlier calculation to the present calculation.

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A=10.31cm/s^2

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• What is the percent error in each?

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

10/10.31=97%accurate = 3% error on both

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You'll need to correct your calculation of acceleration before correcting this.

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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 only in time therefore there is 3 percent error in all numbers. In other words there is no compounding error. So all numbers we get from this data will be 3 percent error.

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

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

They are not different.

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*#&!

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The percent errors are in fact different.

You'll be able to correct this easily.

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