#$&*
Phy 231
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: ->->->->->->->->->->->-> :
(12*3)+(8*3)=60cm/s
@& 12 * 3 would be 12 cm/s * 3 s, which would be 36 cm. This would be the displacement of an object moving at a constant 12 cm/s for 3 s.
Your 8 * 3 corresponds to 8 cm/s^2 * 3 s, which is equal to 24 cm/s. This is the change in the velocity of an object whose acceleration is 8 cm/s^2, during a time interval lasting 3 s.
So 12 * 3 and 8 * 3 stand for completely different things, one for a displacement or change in position, the other for a change in velocity. The units of these quantities are different, so they aren't like terms and cannot be added.*@
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Assuming that acceleration is constant, what will be its average velocity during this interval?
answer/question/discussion: ->->->->->->->->->->->-> :
(60+12)/2=36cm/s
@& This would be correct, if 60 cm/s was the final velocity; however you should include the units with your quantities and carry them throughout the calculation.*@
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How far will it travel during this interval?
answer/question/discussion: ->->->->->->->->->->->-> :
36cm/s*3s=108cm
@& This is based on an erroneous average velocity, resulting from the error in finding the final velocity. However if 36 cm/s was the average velocity, this would be correct.*@
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10 min
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@& You're on the right track but you need to include units and carefully identify your quantities, and the meanings of your calculations. You made a fundamental error early in the process that would probably have been avoided had you included units and identified your quanities.
This shouldn't be difficult for you to correct.
See my notes.
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions 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.
If my notes indicate that revision is optional, use your own judgement as to whether a revision will benefit you. &#
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