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  2. I have a doubt, kindly clarify. - Work Energy and Power - JEE Main
# Engineering

Consider a rubber ball freely falling from a height h =4.9\: m onto a horizontal elastic plate. Assume that the duration of collision is negligible and the collision with the plate is totally elastic. Then the velocity as a function of time and the height as function of time will be

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Option 4)

Answers (1)
A Aadil Khan

As we learnt in

If only conservative forces act on a system, total mechnical energy remains constant -

K+U=E\left ( constant \right )

\Delta K+\Delta U=0

\Delta K=-\Delta U

-

 

 As the ball fall its velocity increases v=\sqrt{2gh}=gt (in\ negative\ direction)

as it reflect after collistion v=v_{0}-gt.

So velocity is linear.

Increasing while going down and decreasing while going up.

h=h_{0} -\frac{1}{2}gt^{2}(going\ down)\ parabolic

h=\frac{1}{2}gt^{2}(going\ up)\ parabolic

So correct graph is 3


Option 1)

This is an incorrect option.

Option 2)

This is an incorrect option.

Option 3)

This is the correct option.

Option 4)

This is an incorrect option.

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