Halliday, Resnick & Walker — Center of Mass and Linear Momentum: Problem 71

71 In Fig. 9-21, projectile particle 1 is an alpha particle and target particle 2 is an oxygen nucleus. The alpha particle is scattered at angle \(\theta_1 = 64.0^\circ\) and the oxygen nucleus recoils with speed \(v_2 = 1.20 \times 10^5 \text{ m/s}\) and at angle \(\theta_2 = 51.0^\circ\). In atomic mass units, the mass of the alpha particle is 4.00 u and the mass of the oxygen nucleus is 16.0 u. What are (a) final and (b) initial speeds of the alpha particle?