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Phy 201
Your 'cq_1_05.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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The problem:
A ball accelerates at 8 cm/s^2 for 3 seconds, starting with velocity 12 cm/s.
• What will be its velocity after the 3 seconds has elapsed?
answer/question/discussion: ->->->->->->->->->->->-> :
final velocity= -12cm/s
aAve= `dv/`dt
8cm/s^2 = (12cm/s - x) / 3s
3s*(8cm/s^2) = ((12cm/s - x) / 3s) *3s
24cm/s = 12cm/s - x
24cm/s - 12cm/s = -x
12cm/s = -x
x= -12cm/s
@& The change in velocity from initial to final would be x - 12 cm/s, not 12 cm/s - x. The change in a quantity is (final value - initial value).
Thus x - 12 cm/s would indicate the change from an unknown initial velocity to a 12 cm/s final velocity.
Your algebra is correct for the equation you wrote; the solution -12 cm/s would be the initial velocity if the final velocity was +12 cm/s.
In the present case the final velocity is 36 cm/s, which you can verify solves the equation corresponding you get if you use x - 12 cm/s.
If the acceleration was -8 cm/s^2, then starting at 12 cm/s you would end up at -12 cm/s.*@
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• Assuming that acceleration is constant, what will be its average velocity during this interval?
answer/question/discussion: ->->->->->->->->->->->-> :
Its average velocity will be 0. (-12cm/s + 12cm/s) /2 = 0
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• How far will it travel during this interval?
answer/question/discussion: ->->->->->->->->->->->-> :
It will travel 4cm. (12cm/s * 3s = 4cm).
@& 12 cm/s * 3 s = 36 cm, not 4 cm.
However if the average velocity was 0 the displacement would be 0 cm/s * 3 s = 0 cm.*@
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15min.
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&#See any notes I might have inserted into your document, and before looking at the link below see if you can modify your solutions. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your old and new solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#