cq_1_011

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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):

Confused about what's being asked in definition above. I took 10cm/4 seconds for the rate of first (A) and 10cm/5s for B, I have 2.5cm/s divided by 2.0 cm/s = 1.25

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The definition does not involve the rate of A or the rate of B. It involves the change in A and the change in B.

You need to identify the A quantity and the B quantity.

The definition tells you how to find the rate of change of A with respect to B.

You are asked to find the rate of change of position with respect to clock time.

What threrefore is the A quantity, and what is the B quantity?

What is the change in the A quantity?

What is the change in the B quantity?

What therefore is the rate of change of the A quantity with respect to the B quantity?

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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):

30cm/3s = 10 cm/s.

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You appear to have applied the definition correctly to this problem, except for a glitch with the units.

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``The units of your calculation are not correct.The units associated with the calculation 40 - 10 are not cm. It they were then, because the units of the denominator are seconds, the units would come out cm/sec. However that is not the case here.Please correct the units of your calculation. The units need to be used throughout the calculation, at every step.

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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):

50 cm

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`` You are given the rate of change of position with respect to clock time.What is the A quantity, and what is the B quantity, in the definition of the average rate of change?How are the changes in the A and B quantities related to the average rate of change?You know the change in one of the two quantities. Which is it?How do you therefore use the definition to find the change in the other quantity?

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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 don't know since I don't understand the definition above.

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It will be very important for you to understand this definition.

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