Wikijunior:How Things Work/Lever
From Wikibooks, the open-content textbooks collection
A lever is an object that is used with a pivot point, or 'fulcrum', to multiply the force applied to another object. Levers are often long and skinny and made of rigid material. Levers are one of the six simple machines.
Contents |
[edit] Who invented it?
It is impossible to say who invented the first mechanical lever. Human beings have used levers since the stone age.
+ was used by zee egyptians to mayke dee pyramidz!
[edit] What does it do?
A lever usually is used to move or lift objects. Sometimes it is used to push against objects, but not actually move them.
[edit] How does it get power?
The power of levers comes from a mechanical advantage. The lever allows less effort to be expended when moving an object, but there's a trade-off. The object will move a shorter distance than the person or thing exerting the force.
[edit] How does it work?
The lever has two important parts. The lever itself and the fulcrum. The placement of the fulcrum determines how far the levered object will move, and how much force is required to move it.
If a weight was resting on a lever a person could lift the weight by pressing on the lever on the other side. The farther away from the fulcrum that person pressed, the less force that person would need to apply. In order to lift the weight the same distance, the force would have to be applied over a longer distance. In science, we call how much effort it takes to move something a certain distance "work." With a lever, you always do the same amount of work no matter how long your lever is. But if you are moving the lever further, then you don't have to push as hard to do the same amount of work. This is also how pullies work, which are just a special kind of lever.
[edit] How dangerous is it?
Levers can be dangerous because they multiply force. There are weapons that are levers including nunchucks, catapults, and atlatls.
[edit] How does it vary?
There are actually three types of levers! They are called first-class levers, second-class levers, and third-class levers.
A see-saw is an example of a first-class lever. In a first-class lever the fulcrum is located between the force pushing down- the input force-(on a see-saw that would be the person going down) and the output force (the person going up). A baby stroller is an example of a second-class lever. In a second class lever, the resistance is located between the effort and the fulcrum. the effort would be the handles of the stroller, where you need to push the stroller in order for it to move. the resistence would be the heaviest part of the machine, the seat where the baby would be. Because you are moving the baby, the baby is the resistance. The fulcrum is the part where it balances the machine, being the wheels. A baseball bat is an example of a third-class lever. In a third class lever the effort and the resistance, the effort being you swinging the bat at the handle and the heavier part of the bat as the resistance, because you need to put effort on it to lift it.
[edit] How has it changed the world?
The lever has changed the way we work immensly. It has helped us to do more work with less resources.
