Hi, I've been trying to figure out this problem for a while now and I could use some help. The problem reads "An electron and proton attract each other with a [tex]1/r^2[/tex] electric force, just like the gravitational force. Suppose that an electron moves in a circular orbit about a proton. If the period of motion is 24 hours, what is the radius of the orbit?" My train of thought so far has been that I would need to equate the [tex]1/r^2[/tex] to the equation for centripetal force [tex]F=mv^2/r[/tex], and solve that for r. I also know that the period comes into play, so I'm guessing that [tex]T=2\Pi r/v[/tex] would also be used somehow. However, I can't figure out how I would solve for the velocity just by plugging in the period to that equation, since they don't give us the value for the radius, and I need the value of the velocity to solve for the radius in the force equation. Am I on the right track or totally off?