Question

Two billiards balls are resting on a smooth table, and just touching. A third identical ball moving along the table with velocity v perpendicular to their line of centres strikes both balls simultaneously. Find the velocities of the three balls immediately after impoact, assuming that the collision is elastic.

Answer 1

given

Two billiards ball

A third identical ball

here collision is elastic so

using the conservation of momentum

we have,

m u = 2 m v cos30^o

u = 2 v cos30^o

u = 2 x v x 0.866

u = 1.732 v

or

u = 1.732 v

so the velocities of the three balls immediately after impact is

u = 1.732 v

and

u = 1.732 v