cq_1_021

phy 121

Your 'cq_1_02.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

** **

The problem:

A ball starts with velocity 4 cm/sec and ends with a velocity of 10 cm/sec.

• What is your best guess about the ball's average velocity?

answer/question/discussion: 7 cm./sec.

• Without further information, why is this just a guess

answer/question/discussion: ? It is half way between 4 and 10

• If it takes 3 seconds to get from the first velocity to the second, then what is your best guess about how far it traveled during that time?

answer/question/discussion: 7cm./sec. for 3 sec.= 21 cm.

• At what average rate did its velocity change with respect to clock time during this interval?

answer/question/discussion: 6 cm/3 sec=2cm per sec.

No quantity in this problem is equal to 6 cm. However, I believe you are doing the right thing and your error is only one of units.

The correct result would be ave rate = (change in velocity) / (change in clock time) = (6 cm/s) / (3 s) = 2 cm/s^2.

** **

5 min. or so

** **

Very good, but you made a significant hair with your units on the last part of the calculation. Be very sure you understand my note, as I believe you will.