30. Rotational Acceleration

This simple device graphically illustrates the concepts of torque and rotational inertia. Movable masses are positioned on a rod which is rotationally accelerated by a falling weight. The rod arm accelerates rapidly when the masses are moved in toward the center but much more slowly when the masses are adjusted out to the ends of the rods so that the rotational inertia is large. Two devices are available so that the class can directly compare the cases of large and small rotational inertia.