## Essential University Physics: Volume 1 (4th Edition)

We know that the gravitational potential energy is: $\frac{GMm}{r}$. We set this equal to kinetic energy, since the radius of the earth is essentially negligible compared to infinite distance: $\frac{GMm}{r}=\frac{1}{2}mv^2$. $v = \sqrt{\frac{2GM}{r}}$ This is more than the escape speed, which is $\sqrt{\frac{2GM}{r}}$.