#$&*
course PHY 121
3.12.11 at 6:10pm
cq_1_071#$&*
PHY121
Your 'cq_1_07.1' report has been received. Scroll down through the document to see any
comments I might have inserted, and my final comment at the end.
** **
A ball falls freely from rest at a height of 2 meters. Observations indicate that the ball
reaches the ground in .64 seconds.
Based on this information what is its acceleration?
answer/question/discussion: ->->->->->->->->->->->-> :
2m/0.64sec = 3.125m/s
a=3.125m/sec/0.64sec = 4.882m/sec^2
##### I used 3.125m/sec because v0=0 in this case. THe change in velocity would be the same
as vAve, right?#####
@& If the initial velocity is 0 and the final velocity is, say, 10 cm/s, then what is the average velocity?
Is the average velocity equal to the final velocity?
It should be clear that it is not.
How are the final and average velocities related when the initial velocity is zero?*@
@& Acceleration is based on change in velocity, not aveage velocity.*@
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Is this consistent with an observation which concludes that a ball dropped from a height of
5 meters reaches the ground in 1.05 seconds?
answer/question/discussion: ->->->->->->->->->->->-> :
5m/1.05se=4.762m/sec
a=(4.762m/sec)/1.05sec = 4.535m/sec^2
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Are these observations consistent with the accepted value of the acceleration of gravity,
which is 9.8 m / s^2?
answer/question/discussion: ->->->->->->->->->->->-> :
No, these figures are significantly lower than the accepted value, assuming they are
correct.
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** **
10 minutes
** **
Are my calculation correct? If not, what did I do wrong?
@& See my note. You used average velocity where you should have used the change in velocity.
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy
of this document with revisions and/or questions, and mark your insertions with &&&& (please
mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
If my notes indicate that revision is optional, use your own judgement as to whether a
revision will benefit you.
&#
*@"
Self-critique (if necessary):
------------------------------------------------
Self-critique rating:
________________________________________
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@& Average and final velocities will not be equal in this situation.
See my note and see if you can answer the questions I pose, and use your reasoning to revise your solution to the given problem.
Please indicate new revisions using &&&&.*@