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?
o vf = 20 cm / 2 s = 10 m/s
o vAve = (0 m/s + 10 m/s) / 2 = 10 m/s / 2 = 5 m/s
o aAve = (10 m/s – 0 m/s) / (2 s – 0s) = 10 m/s / 2 s = 5 m/s^2
change in velocity is not vAve - v0.
answer/question/discussion: ->->->->->->->->->->->-> :
• 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 – 0.06 s = 1.94 s
vf = 20 m / 1.94 s = 10.31 m/s
aAve = (10.31 m/s – 0 m/s) / (1.94 s – 0s) = 10.31 m/s / 1.94 s = 5.31 m/s^2
• What is the percent error in each?
answer/question/discussion: ->->->->->->->->->->->-> :
There would be 3% of error in vf. And 6% of error in aAve.
• If the percent error is the same for both velocity and acceleration, explain why this must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
Then both vf and aAve would be the same.
• If the percent errors are different explain why it must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
If vf and aAve are different from one another then the percent of error would be different.
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30 minutes
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Good. You got the percent error correct. You did have an error in calculating average acceleration.
&#Please compare your solutions with the expanded discussion at the link
Solution
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