Question

The electronic energy of ground state of hydrogen atom works out to be -1.312 . 10^6

Answer 1

From this equation, you can figure out what the velocity and the radius of this electron would be in that particular orbit.

Now, the centripetal force the electron experiences has to be supplied by the Coulomb interaction between the nucleus and the electron - there's absolutely no other way out! Once again, mathematically, this is:

mv2/r=ke2/r2 (2)