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course phy 121

The problem: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:

If the ball accelerates at 8 cm/s^2 for 3 seconds with the starting velocity of 12 cm/s, the velocity after the 3 seconds will be:

a=(vf-v0)/(tf-t0)

8cm/s^2 = (vf-12cm/s)/3s

8cm/s^2(3s) = vf - 12cm/s

24cm/s +12cm/s = vf

36cm/s =vf

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• Assuming that acceleration is constant, what will be its average velocity during this interval?

answer/question/discussion:

vAve= vf+v0 / 2

vAve = 36cm/s +12cm/s / 2

vAve = 48cm/s / 2

vAve= 24cm/s

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• How far will it travel during this interval?

answer/question/discussion:

vAve = displacement/time elapsed

24cm/s = xf-x0 / 3s

24cm/s(3s) = displacement

72cm = displacement

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