Rack and pinion

A rack and pinion is like a toy car steering wheel. You know how when you turn the steering wheel, the little wheels on the car turn too? That's kind of how it works.

Here's the deal: say you have a really long stick (we'll call it the "rack") with teeth on it. Then, imagine taking one of your toy car wheels (we'll call it the "pinion"), and sticking it right up next to the teeth on the rack.

If you turn the pinion, it will slide the rack over a little bit. And if you keep turning the pinion, the rack will keep moving too. So if you attach the rack to something else that needs to move – like a car's wheels – then turning the pinion will make the rack move back and forth, which will in turn make the wheels turn.

So basically, a rack and pinion is a way to turn motion into steering. When you turn the steering wheel, it makes the pinion turn, which makes the rack move, which makes the wheels turn. And that's how you steer a car!