That extra speed, enough to sustain a stable orbit, makes all the difference! We need to compute the speed on a circular orbit, to keep things simple. The radial acceleration is equal to the pull of gravity:
$$ m\frac{\Delta v}{r_f} = \frac{GMm}{r_f^2},$$
which results in the ultra-classic
$$ \Delta v = \sqrt{\frac{GM}{r_f}}.$$