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Phy 231
Your 'cq_1_02.1' 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_02.1_labelMessages.txt **
The problem:
A ball starts with velocity 4 cm/sec and ends with a velocity of 10 cm/sec.
What is your best guess about the ball's average velocity?
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
My best guess would be the velocity that's halfway between the lower velocity indicated and the higher velocity given, which would be 7cm/sec.
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Without further information, why is this just a guess?
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
This is just a guess because we don't actually know what is happening during that interval. It could be steadily increasing from 4cm/sec to 10cm/sec at a consistent rate, which would make 7cm/sec the actual average. But it could also be rolling along at 4cm/sec for almost the entire interval, and then encountering some force that causes it to increase rapidly at the very last second, which would mean the average velocity is closer to 4cm/sec. It could even stop entirely and change direction during that interval.
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If it takes 3 seconds to get from the first velocity to the second, then what is your best guess about how far it traveled during that time?
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
If we are assuming an average velocity of 7cm/sec, we calculate total distance by using our formula for average velocity:
vAve=`ds/`dt
in this case, we have assumed a value for vAve and are given `dt, so we rearrange to solve for `ds.
(vAve)(`dt)=`ds
(7cm/sec)(3sec)=`ds
21cm=`ds
Our best guess is that it traveled 21 cm.
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At what average rate did its velocity change with respect to clock time during this interval?
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
rate of change in velocity = (change in velocity)/(change in time)
=(10cm/sec-4cm/sec)/3sec
=(6cm/sec)/3sec
=2cm/sec^2
Velocity changed by an average of 2cm/sec every second during this interval.
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*#&!
&#Very good responses. Let me know if you have questions. &#