Sometimes, though, air can be used to reduce friction between surfaces. Engineers investigate ways to use air to move objects easily. Engineers design gears to move parts of a machine. Engineers investigate how gears of different sizes make each other turn. 25 Minutes Engineers use gears to make parts of clocks, cars, and other machines move at different speeds.
Motion speeds up if a large gear turns a small gear.
Engineers decide which order gears should be in and which direction they should turn to move machine parts. For example, bicycle pumps, air hammers, and automobile brakes all use compressed air. Engineers also investigate using compressed air to make flying machines such as helicopters. For example, airplane wings have flaps that increase drag to help the plane slow down when landing. 3-6 Hours Engineers investigate how clean drinkable water can be obtained from brackish water using only the sun's energy.