Acceleration due to gravity

Under Newtonian gravity, the gravitational field strength, or gravitational acceleration, due to a point mass M is given by ${\vec {g}}=-G{\frac {M}{r^{2}}}{\frac {\vec {r}}{r}}$. The modulus of g is $|g|=G{\frac {M}{r^{2}}}$.

Here G is the gravitational constant, G = 6.67428×10^-11 Nm²/kg², ${\vec {r}}$ is the position vector in the field, relative to the point mass M, and has a magnitude r.