Two identical ball bearings in contact with each other and resting on a frictionless table is hit head-on by another ball bearing of the same time moving initially with a speed \(v\) as shown in the figure.

 

If the collision is elastic, which of the following (figure) is a possible result after collision?

1. 2.
3. 4.
(b) Hint: Apply the concept of conservation of momentum.

Step 1: Find the final velocities of the balls.

When two bodies of equal masses collide elastically. their velocities interchanged.
When ball 1 collides with ball-2, then the velocity of ball-1 becomes zero and the velocity of ball-2 becomes v, i.e., similarly.

v1=0v2=v

when ball 2 collides will be 3 v2=0,v3=v