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Phy 121
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: ->->->->->->->->->->->-> :
'ds=20 cm
v_0=0
'dt=2 seconds
vAve=(20 cm/2 sec)
= 10 cm/sec
v_f=2vAve
v_f=2 *10 cm/sec
v_f=20 cm/sec
a='dv/'dt
a=(20 cm/sec-0 cm/sec)/2sec
a=10 cm/sec^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: ->->->->->->->->->->->-> :
3% longer--> 0.03*2 seconds= 0.06
0.06 seconds+2 seconds=2.06 seconds
vAve=20 cm/2.06 sec=9.709 cm/sec
v_f=2*vAve
=2*9.709 cm/sec
=19.417 cm/sec
a='dv/'dt
=19.417 sm/sec/ 2.06 sec
=9.426 cm/sec^2
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• What is the percent error in each?
answer/question/discussion: ->->->->->->->->->->->-> :
Velocity percent error as shown above is 3%, for acceleration the change in velocity is 3%, hen you must divide by the time interval (about 3%) so a total of 6%
?????could you elaborate more on this, I believe I got the correct answer
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We would expect 3% and 6% errors, for the reasons you give.
The actual error you obtained are very close to these expected results.
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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 percent error is not the same for both acceleration and velocity.
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• If the percent errors are different explain why it must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
They are different because the value of acceleration and final velocity are different
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The reason is because you divided once by the time interval to get the velocity, and again to get the acceleration. Each division added 3% to the uncertainty.
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25 minutes
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j
&#Good responses. See my notes and let me know if you have questions. &#