If two objects collide and one is initially at rest (a) is it possible for both to be at rest after collision ? (b) is it possible for any one to be at rest after collision.?

If two bodies collide and one is initially at rest, is it possible for both to be at rest after collision?

If two bodies collide and one is initially at rest, is it possible for any one to be at rest after collision?

If one of the two colliding particles is initially at rest, is it possible for both of the particles to be a rest after collision?

A body P moving with a velocity of 20kms^(-1) collides with another body of Q of the same mass at rest. After collision the velocity of Q if P comes to rest after collision is