When a baseball bat hits a ball not all of the bat's energy is used to move the ball. Some of the bat's energy turns into heat which is a sign of friction. Engineers study ways to improve machines wo more of the energy put into them changes to moving energy for doing work. They give airplanes, cars, and boats shapes that let air flow smoothly around them. 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.