For showing that two bodies, free to roll and having different moments of inertia, will undergo different rates of angular acceleration when acted upon by the same force, which in the case of an inclined plane is the force of gravity. Consists of a solid hardwood cylinder and a hollow brass cylinder of equal mass and like external dimensions, 6x2 inches. If each is released at the same instant on an inclined plane, the wooden cylinder will accelerate faster and reach the end of the incline first because it possesses a smaller moment of inertia. Similarly, if each is given the same initial start on a smooth, level surface, the wooden cylinder will come to rest first. The moments of inertia of the two pieces may be calculated from the formula: I=1/2Mr2 for a solid cylinder and I=Mr2 for a hollow cylinder, where "r" in the latter case is the mean of the inner and outer radii.