This apparatus enables experiments to be performed on rotational motion in general. Weights can be fitted to a rotating rod at marked distances from the centre. A dumbbell-shaped arrangement is thus created; the inertia properties of this arrangement can be changed easily and recalculated. The arrangement is fitted to a low friction ball bearing mounted rotating drum. The system is accelerated by a metal weight attached to a cord wrapped around the drum.
The time taken for the weight to fall is measured using a stopwatch, the moment of inertia of the object can then be determined. The experiment is set up quickly using the wall mounted stands; it is ideally suited to group work for 2-3 persons.