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Phys201
Your 'cq_1_06.1' 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_06.1_labelMessages **
For each situation state which of the five quantities v0, vf, `ds, `dt and a are given, and give the value of each.
• A ball accelerates uniformly from 10 cm/s to 20 cm/s while traveling 45 cm.
answer/question/discussion: ->->->->->->->->->->->-> :
v0 is 10 cm/s or initial velocity
vf is 20 cm/s or final velocity
`ds is 45 cm which is displacement
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• A ball accelerates uniformly at 10 cm/s^2 for 3 seconds, and at the end of this interval is moving at 50 cm/s.
answer/question/discussion: ->->->->->->->->->->->-> :
vf is 50 cm/s
`dt is 3 sec
a is 10cm/s^2
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• A ball travels 30 cm along an incline, starting from rest, while accelerating at 20 cm/s^2.
answer/question/discussion: ->->->->->->->->->->->-> :
`ds is 30cm
v0 is 0
a is 20 cm/s^2
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Then for each situation answer the following:
• Is it possible from this information to directly determine vAve?
answer/question/discussion: ->->->->->->->->->->->-> :
Yes because you have 3 out of 5 components to solve an equation leading you to vAve
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This is a good insight. Once you have the algebra and the units down, this is one of two ways to find the result. This algebraic approach will always find the result when we know three of the five quantities, so given the necessary algebra skills it is a reliable way to find the answer.
However it is not the way of 'direct reasoning', and it doesn't build the physical insight we can achieve through direct reasoning.
By 'directly determine' we mean 'figure out from the definitions'.
In the case of the first situation, where you are given v0, vf and `ds, you can do this.
From the values of v0 and vf we can directly determine the value of vAve, which since acceleration is uniform is the average of v0 and vf.
We can also determine `dv in a way that should be obvious.
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• Is it possible to directly determine `dv?
answer/question/discussion: ->->->->->->->->->->->-> :
Yes you can determine `dv from each of the problems above because you have velocity and time data.
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In the first case you can determine the results by direct reasoning, as indicated in my note.
In one, but not both, of the remaining cases you can do so. In the other you would have no recourse but the equations.
Can you identify which is which, and outline the direct reasoning necessary for the case where it works?
I'll note that you know how to solve the case where direct reasoning doesn't work, using the equations. That is a very significant skill.
&#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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