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course PHY 201
cq_1_021#$&*
PHY 201
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):
I would guess the answer to be 7 cm/sec. What I did is took the average of the two values. 10 cm/sec + 4 cm/sec. 14 cm/sec / 2 = 7 cm/sec
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• Without further information, why is this just a guess?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The answer 7 cm/sec is only a guess because the problem does not give the amount of time the object need to get from 4 cm/sec to 10 cm/sec.
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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):
Now I would say the average velocity would be 2 cm/sec every second.
math.
10 cm/sec - 4 cm/sec = 6 cm/sec = 'ds
3 sec = 'dt
vAve = 6cm/sec / 3 sec = 2 cm/sec every second.
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6 cm/s is not a displacement. A displacement would be measured in meters.
What term do we use for the quantity we get when we subtract the initial velocity from the final?
&&&& v0 -vf = 'dv. the change in velocity. 4 cm/s - 10 cm/s = -6 cm/s &&&&
And what quantity do we get when we divide that quantity by the change in clock time?
&&&& once the change in velocity is divided by the change in clock time we get the average velocity. -6 cm/s / 3 s = -2 cm/s/s
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You already determined that the average velocity is 7 cm/s. So this isn't the average velocity.
You've divided change in velocity by change in clock time, which gives you the average rate of change of velocity with respect to clock time, also called acceleration.
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That quantity is not the average velocity. For this question, what is the average velocity, and what therefore is the displacement?
&&&& the average velocity = -2 cm/s/s and therefore the displacement = is 9 cm/s
I calculated displacement with the following
x = .5 (v + v0) t
x = .5 (2 cm/s/s + 4 cm/s) 3s = 9 cm/s
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-2 cm/s isn't average velocity.
In any case none of the quantities in the equation you used represent average velocity.
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I am not sure if my units are correct of even if this is the right equation to be using. &&&&
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I don't like that equation in the form you're using it because the meaning of t is ambiguous, but that is the equation in the book. If all the quaitites are interpreted correctly it would work in this situation.
However at this point you are supposed to be reasoning things from the definitions.
In Assignment 6 you'll be introduced to some equations, equivalent to those in the text but more specific, after you get used to what these quantities mean.
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How is the change in position related to average velocity and change in clock time?
What therefore is the change in position in this situation?
Note that displacement is change in position.
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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):
The object changed velocity every second, increasing how fast it went by two units. this we can see from the previous answer.
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*#&!
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You are definitely doing some of the right operations, but you aren't always identifying them correctly.
&#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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You need another revision on some of these questions. I've inserted more extensive notes.
&#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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