The hydrogen atom consists of a proton of mass 1.67 x 10-27 kg and an orbiting electron of mass 9.11 x 10-31 kg. In one of its orbits, the electron is 5.3 x 10-11 m from the proton. What is the mutual attractive force between the electron and proton?
A planet is discovered to orbit around a star in the galaxy Andromeda, with the same orbital diameter as the Earth around our Sun. If that star has 4 times the mass of our Sun, what will the period of revolution of that new planet be, compared to the Earth's orbital period?
