In this experiment tw0 5/8th inch steel rods form an inclined plane. The rods are about a meter long and are separated by four inches. A meter stick is mounted along side of each rod slightly below its top surface. For most observations the plane is inclined .04 to .06 radians. Angular acceleration is mensured by using a 9 inch diameter disc that is mounted on a 5/16 inch axle. As the disc rolls down the rails it acquires predominantly rotational kinetic energy. The students measure the time required for the disc to rotate to an angle of π, 2π, 4π etc. Through these observations they become familiar with the meaning of the expression θ = αt². In the second part of the experiment the students roll a variety of discs down the plane. In each case (examples of which are a large disc, a rim, and a square pyramid) the object is mounted on a 5/16" steel axle. The students can measure the time required for the axle to travel a given distance along the rails. From these measurements they can determine the moment of inertia of the rotating object. The wheels must, of course, be very carefully balanced.