The diagram depicts a particle $P$, moving with speed $v$, just before it collides with a particle $Q$ at rest and of the same mass. The collision is perfectly elastic. Which statement describes the motion of $P$ and of $Q$ immediately after the collision?
- AP and Q both travel in the same direction with speed $\frac{1}{2}v$.
- BP comes to rest and Q acquires speed $v$.
- CP rebounds with speed $\frac{1}{2}v$ and Q acquires speed $\frac{1}{2}v$.
- DP rebounds with speed $v$ and Q remains stationary.