## University Physics with Modern Physics (14th Edition)

The magnitude of the force that one atom exerts on the other is $6\frac{C^6}{x^7}$. This force is attractive.
$U(x) = \frac{-C^6}{x^6}$ $F = -\frac{dU}{dx}$ $F = -6\frac{C^6}{x^7}$ The magnitude of the force that one atom exerts on the other is $6\frac{C^6}{x^7}$. The negative sign means that this force is attractive.