Really Hard(for me) head on collision question

[ZxcvbnM2000]

Homework Statement

A snooker ball hits another one of the same mass head-on.If a quarter of the initial kinetic energy is dissipated in the collision ,what is the coefficient of restitution?

Homework Equations

E_i=E_f

The Attempt at a Solution

Energy statement:
^u_a+^u_b=(3/4)*(^V_a+^V_b)

Momentum Conservation:

^u_a+^u_b=^V_a+^V_bCoefficient of restitution:

e=(^V_b-^V_a)/(^u_a-^u_b)

But i cannot go further i have tried everything to get a result...could you please help me ?

The energy statement is wrong but for some reasons i can't put squares on each velocity.

 

[gneill]

Since no specific conditions about initial speeds are given, why not consider the problem in the center of mass frame? Symmetry is your friend

 

[ZxcvbnM2000]

Ah..can you be more specific ? I didn't quite get what you meant ! :p

 

[gneill]

What can you say about the speeds of the balls in their center of mass frame of reference? How does the expression for coefficient of restitution look in that frame? How about kinetic energy?