# Electrostatics, finding velocity

1. Jun 11, 2013

### physics604

1. An electron orbits the nucleus of an atom with velocity v. If this electron were to orbit the same nucleus with twice the previous orbital radius, its orbital velocity would now be

a) $\frac{v}{2}$
b) v
c) 2v
d) $\frac{v}{√2}$

2. Relevant equations

$\Delta$Ek + $\Delta$Ep = 0 ?

3. The attempt at a solution

I'm not really sure how I should start this question. None of the equations I have include both the v and the r variable.

Last edited: Jun 11, 2013
2. Jun 11, 2013

### Staff: Mentor

What is the equation for electrostatic attraction?

3. Jun 11, 2013

### physics604

F = kQ1Q2 / r2

But I don't see how that helps.

4. Jun 12, 2013

### Staff: Mentor

And the equation that we use for centripital force for uniform circular motion? There is a reason that we ask you to list the Relevant Equations...