CAIE A-Level Physics 13.3.1 Derivation of g = GM/r²

Practise deriving g = GM/r² from Newton’s law and field-strength definition, showing assumptions, symbols, units and physical meaning.

Exam points

derive g = GM/r² from Newton’s law of gravitation and the definition of field strength
show the assumptions, symbols and units in the derivation

[Maximum number: 2]

Use Newton's law of gravitation to show that the gravitational field strength g at a distance r away from a point mass M is given by

g=\frac{G M}{r^{2}} .

g=F / m

C1

$F=G M m / r^{2}$

and so
$g=\left[G M m / r^{2}\right] / m=G M / r^{2}$

A1

All question bank results loaded