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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):
Vave = (10+4) / 2 = 7cm/sec
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Without further information, why is this just a guess?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
This is assuming that the change in velocity is constant ( constant accelertation.) With out knowing the rate of change in velocity over the entire time, you cannot do any more than assume.
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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):
Vave = 'ds/'dt
'ds = Vave * 'dt
'ds = 7cm/sec * 3 sec
'ds = 2.33 cm
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7 * 3 is more than 2.33.
Clearly you do need to multiply the quantities, as you indicated in the preceding step, in order for the units to work out.
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allowing for 1 sig fig = 2 cm
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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):
Average Acceleration = 'dv/dt = (10 cm/sec - 4 cm/sec) / 3 seconds = 2 cm/sec^2
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5-10 mins
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Good, but one of your answers does not make sense in terms of the situation or the operation you indicated. See my note, which I'm sure you will understand.
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