Gears, pulleys, wheels, and axles! With Physics Discovery, the first thing you'll discover is just how exciting this science actually is. Construct 12 models and then conduct experiments to learn about basic forces and simple machines. A bicycle teaches about wheels, a freight elevator demonstrates pulleys, and a motion picture machine makes centrifugal and centripetal forces seem so simple. 32-page full-color book provides precise illustrated instructions for all projects and experiments. Thames & Kosmos #626914 for ages 8-11 years.