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## Homework Statement

[PLAIN]http://img686.imageshack.us/img686/8532/phyf.jpg [Broken]

It is observed that the ball always bounces exactly once on each step.

## Homework Equations

s = ut + 1/2at^2

## The Attempt at a Solution

[PLAIN]http://img28.imageshack.us/img28/6678/abccz.jpg [Broken]

So after resolving, horizontal velocity must be always constant as it bounces exactly once on each step and must be 0.30/t ms^-1

So, u*cos(theta) = v*cos(phi) = 0.30(1/t)

And to find e, we form the equation e*u*sin(theta) = -v*sin(phi)

I also find time t, for which the ball moves -0.20m vertically and 0.30m horizontally. Upwards as positive. Using s = ut + 1/2at^2

-0.20 = v*sin(phi)*t + 1/2(-9.81)(t^2)

But I tried manipulating around and I just can't find e.

Is something wrong with my method? Do I need to use momentum to calculate this question?

Thank you.

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