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Phy 121
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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 = 20 cm / 2 s = 10 cm/s
v0 = 0 cm/s
vf = 10 cm + 2 - 0 cm/s = 20 cm/s
aAve = (20 cm/s - 0 cm/s) / 2 s = 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: ->->->->->->->->->->->-> :
2 s * 97% = 1.94s
vAve = 20 cm / 1.94 s = 10.31 cm/s
v0 = 0 cm/s
vf = 10.31 cm * 2 - 0 cm/s = 20.62 cm/s
aAve = (20.62 cm/s - 0 cm/s) / 2 s = 10.31 cm/s^2
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• What is the percent error in each?
answer/question/discussion: ->->->->->->->->->->->-> :
20.62 cm/s / 20 cm/s = 1.031 or 3.1% or 3% difference
10.31 cm/s^2 / 10 cm/s^2 = 1.031 or 3.1% or 3% difference
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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: ->->->->->->->->->->->-> :
Acceleration is based off of change in velocity, so whatever percentage you are off in the final velocity, you will have that same percent change in the change in velocity which will show in the acceleration.
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• If the percent errors are different explain why it must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
I think they would have to be the same in this case.
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*#&!
@& The time interval is no longer 2 seconds, it is now 1.94 seconds.*@
@& You failed to use the new times in your calculations of acceleration.
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