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Phy 121
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: ->->->->->->->->->->->-> (start in the next line):
My best guess would be 10cm/sec - 4cm/sec = 6cm/sec / 2 = 3cm/sec
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The ball's minimum velocity appears to be 4 cm/s, and if so its average velocity can't be 3 cm/s. Average velocity can't be less than minimum or greater than maximum velocity.
So without additional information, 3 cm/s isn't a reasonable estimate.
Note that the average of two quantities is not related to their difference. For example the average of 100 and 102 isn't 2.
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Without further information, why is this just a guess?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
I'm only given two points of reference. I don't know how many seconds it took to get from 4cm to 10cm.
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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: ->->->->->->->->->->->-> (start in the next line):
Now I know that the object traveled 2 cm/s. Change in position is 6cm, change in time is 3 seconds. So if it traveled at 2 cm/s for 3 sec then it went 6 cm.
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You don't say how you got 2 cm/s.
If the average velocity was 2 cm/s, this would be a valid argument.
However 2 cm/s appears to be less than the minimum velocity.
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At what average rate did its velocity change with respect to clock time during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Its velocity changed at a rate of 2cm/sec.
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Again you haven't detailed how you got 2 cm/s.
cm/s is not a valid unit for rate of change of velocity, but you might well have arrived at it using a valid process.
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I think you're on the right track, but you do need some revision and clarification.
&#Please see my notes and submit a copy of this document with revisions, comments 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. &#
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