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PHY 201
Your 'cq_1_03.1' 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_03.1_labelMessages.txt **
The problem:
A ball starts with velocity 0 and accelerates uniformly down a ramp of length 30 cm, covering the distance in 5 seconds.
What is its average velocity?
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
30cm/5sec = 6cm/sec v_ave
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If the acceleration of the ball is uniform then its average velocity is equal to the average of its initial and final velocities.
You know its average velocity, and you know the initial velocity is zero.
What therefore must be the final velocity?
answer/question/discussion: ->->->->->->->->->->->-> n/discussion (start in the next line):
(0cm/sec + x)/2 = 6cm/sec; x = 12cm/sec; vf = 12cm/sec
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By how much did its velocity therefore change?
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
vf - v0 = 12cm/sec
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At what average rate did its velocity change with respect to clock time?
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
vf/'dt = 12/ 5 =2.4 cm/ sec
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An average rate of change of velocity with respect to clock time is
ave rate = (change in velocity) / (change in clock time),
not final velocity / change in clock time.
The initial velocity is zero so the change in velocity is the final velocity, but you want to keep your thinking close to the definition.
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You haven't included units in your calculation, and the units of your result are incorrect. (The numbers are correct.)
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What would a graph of its velocity vs. clock time look like? Give the best description you can.
answer/question/discussion: ->->->->->->->->->->->-> scussion (start in the next line):
With velocity as the y-axis and time as the x-axis. It would be a linear line rising from (0,0) to (12,5)
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Good, but the coordinates of a velocity vs. clock time graph can be expressed by ordered pairs, with clock time first and velocity second. You've got them backwards.
You also need to include the units with any quantity that has units.
So the (12, 5) should be (5 sec, 12 cm/sec).
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Good work, but you need to make a couple of minor but very important modifications.
&#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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