Your 'cq_1_05.1' 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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A ball accelerates at 8 cm/s^2 for 3 seconds, starting with velocity 12 cm/s.
• What will be its velocity after the 3 seconds has elapsed?
answer/question/discussion: vf=vi+a*t = vf=12+8*3 =36
• Assuming that acceleration is constant, what will be its average velocity during this interval?
• answer/question/discussion: (36-12)/3= 8
This cannot be the average velocity.
The initial velocity on this interval is 12 cm/s, and the final is 36 cm/s.
The average velocity will lie between the initial and final velocities.
The average velocity is not equal to 12 cm/s or to any lesser velocity.
Subtraction is not used in the process of averaging two numbers. Subtraction is used, in both the numerator and denominator, when finding the average rate of change of one quantity with respect to another.
• How far will it travel during this interval?
answer/question/discussion: vf^2=vi^2+2ax= 1296=144+16x= 1152=16x = 72=x
Your use of the equation isn't bad, but you didn't use units on anything and therefore failed to notice that you were using an acceleration in feet / second^2 with velocities in meters / second.
At this point, however, you should be reasoning out your answers based on the definitions of velocity and acceleration rather than bypassing the 'understanding' phase by using the equations.
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45 min
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You need to understand the definitions of velocity an acceleration, and use them to solve these problems.
Please see my notes and submit a copy of this document with revisions and/or questions, and mark your insertions with &&&&.