A particle P moving with speed v undergoes a head -on elastic collision with another particle Q of identical mass but at rest. After the collision
(a) Both P and Q move forward with speed v/2
(b) Both P and Q move forward with speed v/√2
(c) P comes to rest and Q moves forward with speed v
(d) P and Q move in opposite directions with speed v√2
Answer : c
(6)