Question

An alpha particle has a kinetic energy of about 5 MeV after they are far from the nucleus. Use this information to estimate the size of a nucleu by assuming that the alpha particle leaves the edge of the nucleus with zero kinetic energy and that the electrostatic potential energy is the only potential energy it has at that position. Assume the charge on the nucleus is +88e. The charge on an alpha particle is +2e while the mass of an alpha particle is 4.0026 amu where 1 amu=1.66x10^27 kg.

Answer 1

k*Q1*Q2/R = 5 MeV = potential energy change from R to infinity.
Convert the 5 MeV to Joules and solve for R
k is the Coulomb constant
Q1 = 2e
Q2 = 88e
e = electron charge