course Phy 231
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:
v0 = 4 cm /s
vf = 10 cm/s
vAve = [ 10 cm/s + 4 cm/s ] / 2 = 14 cm/s / 2 = 7 cm/s
Without further information, why is this just a guess?
answer/question/discussion:
this is only a guess because we do not know if the acceleration which took us from 4 cm/s to 10 cm/s was constant or not. We also do not know the distance or time interval over which the ball traveled.
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:
vAve = 'ds / 'dt, therefore: 'ds = vAVe * 'dt
'ds = 7 cm/s * 3 s = 21 cm
At what average rate did its velocity change with respect to clock time during this interval?
answer/question/discussion:
a = 'dv / 'dt = [10 cm/s - 4 cm/s] / 3 s = 2 cm/s^2
This looks good; however I can't tell what's changed from your original submission. When resubmitting, you should insert your comments into a copy of the posted document, and mark your insertions in the requested manner.
No problem in this case; just keep that in mind for future submissions. If I get all the information I can give you better feedback.