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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 the quantity 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):
A: position: 20cm-10cm=10cm
B:clocktime:9sec-4sec= 5 sec
ave rate= 10cm/5sec= 2cm/sec
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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):
A: velocity: 40cm/sec-10cm/sec= 30cm/sec
B: clocktime: 3 sec
Ave rate= 30cm/sec/ 3 sec= 10cm/sec
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If you divide a quantity by seconds, its units will change. So when dividing cm / sec by sec you cannot possibly get cm / sec.
The units calculation is as follows:
(cm/sec) / sec = (cm/sec) * (1/sec) = cm * 1 / (sec * sec) = cm/sec^2.
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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):
ave rate= 5cm/sec
B: clocktime: 10 seconds
5cm/sec=A/10seconds
A(1sec)=5cm*10seconds
A=50cm
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5 cm * 10 seconds = 50 cm * seconds, not 50 cm.
To solve your correct eqution
5cm/sec=A/10seconds
for A, multiply both sides by 10 seconds to get
A = 5 cm/sec * 10 sec = 50 cm * sec / sec = 50 cm.
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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 will write this down to constantly refer back to.
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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):
Average rate of change of A with respect to B = (change in A) / (change in B). First identify quantity A and quantity B and solve for the average rate of change.
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Very good, except for the units calculations.
Check my notes and let me know if you have questions.
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