Chapter 9, Problem 50P

(II) A neutron collides elastically with a helium nucleus (at rest initially) whose mass is four times that of the neutron. The helium nucleus is observed to move off at an angle ${{\theta }^{\prime }}_{\text{HC}}=45°$. Determine the angle of the neutron, ${{\theta }^{\prime }}_{\text{n}}$, and the speeds of the two particles, ${v^{\prime }}_{\text{n}}$ and ${v^{\prime }}_{\text{He}}$, after the collision. The neutron’s initial speed is 6.2 × 10⁵ m/s.