Eisco Center Of Mass Demonstrator - Roller & Ramp - Rolls Up Inclined Plane - Clear Coated Wood Construction, 17'' L - Great AsThis Ingenious Apparatus Makes A Great Physics Demonstration, Executive Gift, Or Desk Toy. Place The Double Cone Roller At The Bottom Of The Inclined Plane And Watch It Travel ''Up'' The Ramp With No Applied Force. The Physics Behind The Demonstration Is That As The Roller Moves Up The Ramp The Center Of Mass Is Actually Moving Downward Which Drives The Roller Up The Ramp Itself. Amaze Your Students And Colleagues. Constructed Of Durable Wood And