Mechanics
Escape velocity from surface gravity
Use the surface gravity and radius, which avoids the gravitational constant entirely.
The Formula
v = sqrt(2 x g x r)
Use the surface gravity and radius, which avoids the gravitational constant entirely.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| v | Escape velocity | metres per second | Required speed at the surface. |
| g | Surface gravity | metres per second squared | Gravitational acceleration at the surface. |
| r | Radius | metres | Distance from the centre of the body to its surface. |
What Each Symbol Means
vmetres per second
Escape velocity
Required speed at the surface.
gmetres per second squared
Surface gravity
Gravitational acceleration at the surface.
rmetres
Radius
Distance from the centre of the body to its surface.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate an escape velocity page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate An Escape Velocity, filed under Science. Every number the guide produces comes from substituting into this one line.