I am going to try traduce the problem in the best way i can. What is the minimum distance that protons of a 1 MeV bundle that collides in a gold leaf can approach to the atom core. Solution: 1.14 x 10-13 m I am posting these problem because i do not have any idea how to start it. So please, do not delete this post because i do not have any attempt to solution. I searched in lot of places and i am not seeing what is the formula to resolve this problem.