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Phy 201
Your 'cq_1_01.1' 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_01.1_labelMessages **
The problem:
Here is the definition of rate of change of one quantity with respect to another:
The average rate of change of A with respect to B on an interval is
• average rate of change of A with respect to B = (change in A) / (change in B)
Apply the above definition of average rate of change of A with respect to B to each of the following. Be sure to identify thequantity A, the quantity B and the requested average rate.
• If the position of a ball rolling along a track changes from 10 cm to 20 cm while the clock time changes from 4 seconds to 9 seconds, what is the average rate of change of its position with respect to clock time during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
(10-20)/(4-9) = 10/5 = 2 cm/s average rate
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• If the velocity of a ball rolling along a track changes from 10 cm / second to 40 cm / second during an interval during which the clock time changes by 3 seconds, then what is the average rate of change of its velocity with respect to clock time during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
(40-10)/3 = 10 cm/sec avg rate
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You are not including units in your calculations.
This calculation would be
(40 cm/s - 10 cm/s) / (3 s) = 30 cm/s / (3 s) = 10 cm/s * 1/s = 10 cm/s^2.
Units need to be included with every quantity which has units.
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• If the average rate at which position changes with respect to clock time is 5 cm / second, and if the clock time changes by 10 seconds, by how much does the position change?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
5 = x/10, x = 50 cm change
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• You will be expected hereafter to know and apply, in a variety of contexts, the definition given in this question. You need to know this definition word for word. If you try to apply the definition without using all the words it is going to cost you time and it will very likely diminish your performance. Briefly explain how you will ensure that you remember this definition.
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
I remember that the average rate of change is calculated by the change of one factor divided by the change in the other factor. I have been introduced to this concept multiple times before and I have it memorized.
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• You are asked in this exercise to apply the definition, and given a general procedure for doing so. Briefly outline the procedure for applying this definition, and briefly explain how you will remember to apply this procedure.
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Applying this definition involves making sure the numerator and denominator are the correct units so that you get the proper proportion (eg. Cm/s not s/cm). I can make sure that this step is done correctly by double chacking my work and my units and do a mental check to make sure that the units of my answer make sense for the problem I am solving.
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You are applying the definitions correctly, but you are not doing the units calculations. See my notes.
You'll get plenty of practice with this over the next few assignments. Just be alert to the need to use units throughout.
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