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PHY 242

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PHY 241

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A 70 gram ball rolls off the edge of a table and falls freely to the floor 122 cm below. While in free fall it moves 40 cm in the horizontal direction. At the instant it leaves the edge it is moving only in the horizontal direction. In the vertical direction, at this instant it is moving neither up nor down so its vertical velocity is zero. For the interval of free fall:

• What are its final velocity in the vertical direction and its average velocity in the horizontal direction?

answer/question/discussion: ->->->->->->->->->->->-> :

`dPE=.07kg*9.8m/s^2*1.22m=0.837J

-0.837J=.07kg*vf^2

Vf=-3.46m/s

`ds=vf/2*dt

1.22m=-3.46m/s/2*dt

`dt=0.705s

vAvey=ds/dt=0.04m/0.705s=0.57m/s

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Average y velocity is -1.73 m/s, the average of its initial and final vertical velocities.

What you have calculated here is the average velocity in the x direciton.

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Most of your results are based on

-0.837J=.07kg*vf^2

You have the right idea here, but KE = 1/2 m v^2 so this should be

-0.837J=1/2 * .07kg*vf^2

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