1. The problem statement, all variables and given/known data The mass of an electron is 9 x 10-31 kg. The mass of a proton is 1.7 x 10-27 kg. The proton and electron are about 1.0 x 10-10 m apart in a hydrogen atom. What force of gravitation exists between the proton and the electron of a hydrogen atom? What is the centripetal acceleration of the electron? 2. Relevant equations Fg = G*m1*m2/d^2 * Fg is the magnitude of the gravitational force between the two point masses, * G is the gravitational constant, * m1 is the mass of the first point mass, * m2 is the mass of the second point mass, * r is the distance between the two point masses. ar = v2 / r ar is centripetal acceleration v is velocity in meters per second, r is the radius of the circle in meters 3. The attempt at a solution I plugged in the infomation to find the gravitational force and got 1.02051 x 10^-47 but it doesn't give us the nessicary information to find the centripetal acceleration... I don't think.. can anyone help me with this?