No battery required, just pull and start! Allow children to visually experience the energy conversion from elastic potential energy to kinetic energy during the hands-on process. Adjustable speed ratio: the gear set switches between 1:2/1:3 gears to compare the speed and torque under different transmission ratios. Experience the four major knowledge points of energy conservation, friction, gear transmission, and air resistance in one go. Designated equipment for school science and technology festival and youth maker competition. Usage scenario: Classroom demonstration: The teacher instantly transforms into a "physics wizard". Family living room: floor racing competition to see who's more scientifically tuned. Outdoor flat ground: Grasslands, squares, and corridors are all suitable for smooth running.