## Conceptual Physics (12th Edition)

This situation is like the train car that collides with an identical stationary one (see Figure 6.14 on page 99). They stick together and move away with half the initial velocity. $$Mv + 0 = (M+M)(\frac{v}{2})$$ The incoming deuteron shares its momentum equally with the other particle, leading us to conclude that it too is a deuteron.