I'm not sure if this will help but...
The velocity of the ball when it hits the ground can be calculated in two ways:
1. At the point where the ball hits the groud the gravitational potential enery (GPE) is zero as: U=mgh and h=0. Therefore the initial gravitational potential energy must have all been converted to kinetic enery (as there is no air resistance, therefore no GPE is converted to heat etc whilst falling). Hence kinetic energy= GPE ie: ½mv²=mgh
So if you know the mass of the ball and the hight from which the ball was dropped from, v can be calculated (using g=9.8)
2. One of the following kinematics equations can be used, depending on the information given:
v=initial velocity (zero in your case)
u=final velocity (what you're trying to find)
a=acceleration (due to gravity for a bouncing ball. approx. 9.8)
Make sure you use negative signs appropriately (ie assign down as negative and up as positive) to make sure you end up with the right answer.
I hope this is helpful. If you have any questions, write to me at [email protected]
(yr 12, australia)