cq_1_021

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Phy 121

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):

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10+4= 14 cm/s

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The velocity never exceeds 10 cm/s, so the average velocity won't be 14 cm/s.

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It does not give us how many seconds it took to get from 4 cm to 10 cm or how long the distance was.

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):

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You will know the average velocity and you are given the time interval. How can you use these quantities to find the displacement?

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The first second in started with a velocity of 4cm/sec.

I am going to guess that at the second, second it went to 7 cm/sec.

The third second was 10 cm/sec.

So adding those up, I got 20cm/ 3 sec.

At what average rate did its velocity change with respect to clock time during this interval?

answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):

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Your thinking isn't quite correct, but it's not unreasonable either.

However to answer this question you have to apply the definition of rate of change.

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You should start by stating the definition of rate of change of A with respect to B.

Then identify which quantity in this question is the A quantity and which is the B quantity.

Then see if you can apply the definition to answer the question.

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&#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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cq_1_021

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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 **

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): 4 cm/s+10 cm/s=14 cm/s / 2= 7cm/s

 

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Without further information, why is this just a guess?

answer/question/discussion: ->->->->->->->->->->->-> (start in the next line): We don’t know how much the ball sped up and slowed down between the beginning and end.

 

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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): `ds=vAve*`dt

 `ds=7 cm/s*3s

`ds=21 cm

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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):

average rate=(change in velocity)/(change in clock time)

change in velocity=10 cm/s-4 cm/s=6 cm/s

change in clock time=3 s

average rate=(6 cm/s)/3 s

average rate=2 cm/sec^2

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Very good.

Note that you need to include your name when you submit your work. You did include the access code so this will post, but I can't familiarize myself with the pattern of your thinking unless I know who you are.

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