1. The problem statement, all variables and given/known data An alpha particle (a helium nucleus, containing 2 protons and 2 neutrons) starts out with kinetic energy of 10.5 MeV (10.5x106 eV), and heads in the +x direction straight toward a gold nucleus (containing 79 protons and 118 neutrons). The particles are initially far apart, and the gold nucleus is initially at rest. Answer the following questions about the collision. What is the initial momentum of the alpha particle? (You may assume its speed is small compared to the speed of light). What is the initial momentum of the gold nucleus? What is the final momentum of the alpha particle, long after it interacts with the gold nucleus? What is the final momentum of the gold nucleus, long after it interacts with the alpha particle? What is the final kinetic energy of the alpha particle? What is the final kinetic energy of the gold nucleus? Assuming that the movement of the gold nucleus is negligible, calculate how close the alpha particle will get to the gold nucleus in this head-on collision. 2. Relevant equations p_f = p_i 1 eV = 1.6e-19 J k = 1/2 mv^2 m_proton/neutron = 1.7e-27 kg q_proton = 1.6e-19 r_proton/neutron = 1e-15 m 3. The attempt at a solution k_i = 10.5e+5 eV 10.5e+5 eV * 1.6e-19 = 1.68e-12 k_i = 1.68e-12 J m_alpha = (2 * 1.7e-27) + (2 * 1.7e-27) m_alpha = 6.8e-27 kg k_i = 1/2 mv^2 1.68e-12 = 1/2 (6.8e-27) (v)^2 v = 2.22e+7 m/s p_alpha,i = mv p_alpha,i = <1.51e-19, 0, 0> kg * m/s m_au = (79 * 1.7e-27) + (118 * 1.7e-27) m_au = 3.349e-25 kg v_au,i = 0 p_au,i = mv p_au,i = <0, 0, 0> kg * m/s r_alpha = cube root 4 * 1e-15 r_alpha = 1.59e-15 m r_au = cube root (79 + 118) * 1e-15 r_au = 5.82e-15 q_alpha = 2 * 1.6e-19 q_alpha = 3.2e-19 q_au = 79 * 1.6e-19 q_au = 1.264e-17 u_elec = 1/4 pi E_0 * q_1 q_2 / r u_elec = 9e+9 * (4.04e-26 / 7.41e-15) u_elec = 9e+9 * 5.46e-22 u_elec = 4.92e-12 J p_f = p_i p_alpha,f + p_au,f = p_alpha,i + p_au,i p_alpha,f + p_au,f = p_alpha,i + 0 (m_alpha * v_alpha,f) + (m_au * v_au,f) = 1.51e-19 6.8e-27 * v_alpha,f + 3.349e-25 * v_au,f = 1.51e-19 ??? I don't know where to go from here to get p_alpha,f . I calculated u_elec because I could, but I don't know how its related to the problem.