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: ->->->->->->->->->->->-> :
'ds=(v0 +vf)/2 * 'dt
20 cm = (0+vf)/2 * 2 s
10 cm/s = vf/2
20 cm/s = vf
vf= v0 +a * 'dt
20 cm/s= 0 + a * 2sec
10 cm/s^2 = a
'ds= vAve * 'dt
20 cm = vAve * 2 s
10 cm/s = vAve
#$&*
If the time interval is in error so that it is 3% longer than the actual time interval, then what are the actual values of the final velocity and acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
s=2.06 s
'ds = (v0 +vf)/2 * 'dt
20 cm = vf/2 * 2.06s
9.71 cm/s = vf/2
19.42 cm/s = vf
19.42cm/s = a * 2.06s
a= 9.43 cm/s^2
You got 10 cm/s^2 for your first result.
This one is 9.43 cm/s^2.
What is the difference, and what is the difference as a percent of your first result?
#$&*
What is the percent error in each?
answer/question/discussion: ->->->->->->->->->->->-> :
I assume 3% but really don't know.
#$&*
If the percent error is the same for both velocity and acceleration, explain why this must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
These variables are dependent on one another so I assume the percent error should be the same for both.
#$&*
If the percent errors are different explain why it must be so.
answer/question/discussion: ->->->->->->->->->->->-> :
I honestly don't know.
#$&*
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Revised: 06 Feb 2010 17:09:18 -0500
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2/15 at 3:45 p.m.
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