holographic projection bear generator power station automatic drawing machine carousel magnetic small aircraft sundial solar fan hydraulic excavator hook roller elevator lift catapult space instrument making clocks lever balance portable power generator peristaltic robot traffic lights automatic serve machine making electric fan conductor detector piano music box solar energy driven car double propeller aircraft solar helicopter newton's cradle ferris wheel balance bird make table lamp vacuum cleaner balance robot money detector wind power generation air floating ball lifting crane hydraulic elevator platform voice control car shooting machine paddle steamer earthquake alarm periscope hydraulic mechanical arm mechanical dog electric gliding aircraft

educational selection experiment