# Help solve all this question please

1. Jun 27, 2013

### tauwee

help solve all this question please...:(

A uniform smooth sphere P,of mass 3m, is moving in a straight line with speed u on a smooth horizontal table.Another uniform smooth sphere Q, of mass and m and having the same radius as P, moving with speed 2u in the same straight line as P but in the opposite direction to P. The sphere P collides with the sphere Q directly. The velocities of P and Q after the collision are v and w respectively, measured in the direction of motion of P before the collision. The coefficient of restitution between P and Q is e.

a) Find an expression for v in terms of u and e.
b) Show that, if the direction of motion and P is changed by the collision, then e>1/3.
c) Find an expression for w in terms of u and e.

Following the collision with P, the sphere Q then collides with and rebounds from a vertical wall which is perpendicular to the direction of motion of Q. The coefficient of restitution between Q and the wall is e'

Given that e=5/9, and that P and Q collide again in the subsequent motion,
e) Show that e'>1/9.

2. Jun 27, 2013

### sjb-2812

Do you know any equations that may help?

3. Jun 27, 2013

### tauwee

this is the prove question...i dont know wht equation can solve :(

4. Jun 27, 2013

### sjb-2812

Can you define " The coefficient of restitution"?