A lever is a simple machine made from a stiff bar that rests on a turning point called a fulcrum. When you push down on one end of the lever, the other end pushes up. Levers help you lift heavy things with less effort by trading how far you push for how much force you get. A seesaw, a bottle opener, and a wheelbarrow are all examples of levers.
Build seesaws using rulers balanced on pencils. Place small weights at different positions and see how moving the fulcrum changes how easy it is to lift them. Use real tools like bottle openers and claw hammers to feel levers in action.
A lever is one of the simplest and most useful machines ever used by people. It is just a stiff bar that balances on a point called the fulcrum. When you push down on one side, the other side goes up. You have used levers your whole life — every time you ride a seesaw, pry open a paint can lid, or use a claw hammer to pull out a nail, you are using a lever.
The magic of a lever is that it lets you lift something heavy without using as much force. Here is the trade-off: you have to push your end a longer distance. Imagine trying to lift a heavy rock with your hands. Hard, right? Now slide a long board under the rock and put a small stone under the board as a fulcrum. Push down on the far end of the board, and the rock rises with much less effort from you. You pushed down a big distance, but the rock only moved up a little.
Where you place the fulcrum makes a huge difference. If the fulcrum is close to the heavy object (the load), you get more lifting power but the load does not move very far. If the fulcrum is farther from the load, you need more effort but the load moves a bigger distance. This is why a seesaw works best when the fulcrum is in the middle and the riders weigh about the same — the distances on both sides are equal, so the forces balance.
Scientists group levers into three classes depending on where the fulcrum, the effort, and the load are located. A seesaw is a first-class lever, with the fulcrum between the effort and the load. A wheelbarrow is a second-class lever, with the load between the fulcrum and the effort. Tweezers are a third-class lever, with the effort between the fulcrum and the load. No matter the class, every lever follows the same big idea: trading distance for force to make work easier.