A 232 Th (thorium) nucleus at rest decays to a 228 Ra (radon) nucleus with the emission of an alpha particle. The total kinetic energy of the decay fragments is 6.54 x 10^-3 J. An alpha particle has 1.76% of the mass of a 228 Ra nucleus. a) Calculate the kinetic energy of the recoiling 228 Ra nucleus. b) Calculate the kinetic energy of the alpha particle. ** Here again I would use the formula k_f = 0.5(m_1 + m_2)v_(partical)^2 now I know we don't have any velocities to work with but the problem gives me the total kinetic energy = 6.54*10^-3 Therefore I should solve maybe for velocities first in order to plug in and get the kinetic energy of Ra and do the same for the alpha particle. Assuming m_1 = 228 and the alpha particle m_2 = 4.0 I need help seeing if I'm going on the right track with finding the velocities of the particles or is that not necessary ?