Collision of Balls - Coefficient of Restitution

[prateek_34gem]

Homework Statement

Two equal balls are in contact on a table and are in equillibrium. A third ball collides with them simultaneously, symetrically and remains at rest after the impact. The coefficient of restitution is :

A)2/3
B)3/2
C)1/3
D)1/2

Homework Equations

The Attempt at a Solution

i have tried by combining the masses and velocities of the two balls at rest then found e. like the collision of two bodies ( considering two bodies as one ) .

 

[LowlyPion]

You have 2 equations that you would satisfy don't you?

Conservation of momentum which gives you the relationship between the initial velocity of the first ball and the final velocity of the second 2.

Then you have the equation for the coefficient of restitution that relates the before and after velocities of the 2 bodies. (This is simplified by the fact that before the collision only 1 was in motion. And after the collision the first becomes stationary.)

 

[prateek_34gem]

but there are two balls lying at rest do i have to consider the motion of only one of thm or take them whole as one ?

 

[prateek_34gem]

i have got e=1/2
but thts wrong ans . Correct ans . is 2/3
is ans given in book wrong or i am wrong ??