An inexpensive strong molded plastic body dynamics cart to demonstrate Newton's third law of motion. Cart fitted with a motor with fan, battery holder and on / off switch. Hard plastic wheels. Removable clear acrylic sail. The plane of the sail when mounted is perpendicular to air flow. Cart without sail 5.5" (140mm) x 2.75" (70mm) x 5.25" (1300m) high. Sail 4.25" (110mm) x 4.25" . Requires two "AA" batteries, not included.