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## Homework Statement

An electron orbits a nucleus which carries a charge of +9.6E-19 C. If the electron's orbit radius is 2.0E-10 m, what is its electric potential energy?

## Homework Equations

Ep = kQ1Q2/r

V = kQ/r

V = Ep/Q

## The Attempt at a Solution

I tried using Ep = kQ1Q2/r

Ep = (9E9)(9.6E-19C)(-1.6E-19C) / (2.0E-10m)

Ep = -6.9E-18 J

the answer key is saying -6.9E-19 J

and V = kQ/r , V = Ep/Q

V = (9E9)(9.6E-19C) / (2.0E-10m)

V = 43.2 V

V = Ep/Q

Ep = 43.2 V x (1.6E-19)

Ep = -6.9E-18 J

the answer key is saying -6.9E-19 J

Am I doing something wrong, or is the answer key off by an exponent?

Thanks,