This is used to quantitatively determine the inertial mass of an object and is a simple way to demonstrate Newton's First Law. You can calculate the periodic motion of the balance when pushed sideways, showing that its motion is independent of the effects of gravity. Includes a frame with two platforms (one with holes) connected by two firm, horizontal spring blades. We also include a cylinder of unknown mass which is suspended by a hook and rests in a hole in the platform. Detailed instructions. You need a clamp, not included.