#$&*
PHY 121
Your 'cq_1_01.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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The problem:
Here is the definition of rate of change of one quantity with respect to another:
The average rate of change of A with respect to B on an interval is
• average rate of change of A with respect to B = (change in A) / (change in B)
Apply the above definition of average rate of change of A with respect to B to each of the following. Be sure to identify the quantity A, the quantity B and the requested average rate.
• If the position of a ball rolling along a track changes from 10 cm to 20 cm while the clock time changes from 4 seconds to 9 seconds, what is the average rate of change of its position with respect to clock time during this interval?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The change in distance is 10 cm divided by the change in time which is 5 equals 2.
#$&*
@& You included the units of the change in position. The change in time also has units, as does the final result.*@
• 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):
The average rate of change in velocity is 10 cm/s.
#$&*
@& The number is correct but the units are not.
You need to state what quantity was divided by what quantity, including units. The final result then has the units that follow from the units of your two quantities.*@
• If the average rate at which position changes with respect to clock time is 5 cm / second, and if the clock time changes by 10 seconds, by how much does the position change?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
The position change is 50 cm. You can get this by multiplying 10 by 5.
#$&*
@& 10 * 5 = 50, not 50 cm.
10 cm/s * 5 sec = 50 cm.*@
@& Good but you do need to include units with every quantity that has units.*@
@& See my notes.*@