(a) State Newton’s law of gravity in scalar form and vector
form.
(b) State how potential energy and forces in 1D are related and use
this to determine an expression for the gravitational potential
energy, choosing an appropriate zero-point.
(c) A thin, 1D homogeneous rod of material has a mass M and length
L. The rod is bent into a semi-circle. Determine an expression for
the strength of the gravitational field at the centre of curvature
of the circular arc.