Mechanics
Newton's law of gravitation
The attractive force between two point masses, or between two uniform spheres.
The Formula
F = G x m1 x m2 / r^2
The attractive force between two point masses, or between two uniform spheres.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| F | Force | newtons | Attractive force in newtons. |
| G | Gravitational constant | newton metre squared per kilogram squared | Universal constant, about 6.6743e-11. |
| m1 | First mass | kilograms | Mass of the first body. |
| m2 | Second mass | kilograms | Mass of the second body. |
| r | Separation | metres | Centre-to-centre distance. |
What Each Symbol Means
Fnewtons
Force
Attractive force in newtons.
Gnewton metre squared per kilogram squared
Gravitational constant
Universal constant, about 6.6743e-11.
m1kilograms
First mass
Mass of the first body.
m2kilograms
Second mass
Mass of the second body.
rmetres
Separation
Centre-to-centre distance.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate a gravitational force 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 A Gravitational Force, filed under Science. Every number the guide produces comes from substituting into this one line.