Question on a ball dropping( conservation of energy)

[Peter-John King]

Homework Statement

A ball of mass 1 Kg is dropped from a height of 7m and rebounds to a height of 4.5m Calculate:
its kinetic energy just before impact
the initial rebound velocity of the ball and kinetic energy. Account for loss of kinetic energy on impact



2. Homework Equations [/B]
i am not sure of all the relevant equations i used pe=mgh and k.e=1/2mv^2

The Attempt at a Solution

I found the answer to a using the formula P.E.=mgh=1x10x7=70J
K.E.=P.E.=70J
I do not know how to find the second answer

 

[Doc Al]

I found the answer to a using the formula P.E.=mgh=1x10x7=70J
K.E.=P.E.=70J

Good.

I do not know how to find the second answer

Use the same equation. (A different height, of course.)