Lever

A lever is a simple machine made from a beam or rigid rod that turns around a fixed point called a hinge or fulcrum. It is one of the six basic simple machines that scientists discovered during the Renaissance. Levers help us do work more easily by making it possible to lift heavy objects or move things with less effort.

The way a lever works depends on where the fulcrum, the load, and the effort are placed. There are three types of levers, each with a different setup. When we use a lever, we trade off moving a smaller distance with more force, or moving a greater distance with less force. This helps us gain what is called mechanical advantage, meaning we can do more work with less effort. Because of this, levers are very useful in many tools and machines, making everyday tasks easier to handle.

Etymology

The word "lever" came into English around the year 1300 from Old French, where it was spelled levier. This word comes from the verb lever, which means "to raise". That verb traces back to Latin, where it was levare, from the adjective levis, meaning "light" (as in not heavy). The root of this word is from a very old language called Proto-Indo-European, where the stem leg^wh- meant "light", "easy", or "nimble". This same root also gave us the word "light" as the opposite of "heavy".

Lever history

Some believe the first lever was the digging stick, used by people long ago. Early signs of levers appear from around 5000 BC in ancient Egypt, where they were used in simple balance scales.

Later, around 3000 BC in Mesopotamia (modern-day Iraq), people created a device called the shadouf, which used levers. In ancient Egypt, workers used levers to lift very heavy stones, even ones weighing more than 100 tons. The famous Greek mathematician Archimedes once said, "Give me a lever long enough and a place to stand, and I shall move the world." This shows how powerful and useful levers can be.

Force and levers

A lever is a beam connected to a fixed point, called a fulcrum, which allows it to pivot. In an ideal lever, there is no loss of energy, meaning the effort you put in equals the force you get out. The relationship between the input force and output force depends on the distances from the fulcrum to where these forces are applied. This is known as the law of the lever.

The mechanical advantage of a lever can be found by looking at the balance of moments or torque around the fulcrum. If the distance the output force travels is greater, the output force will be smaller. The mechanical advantage is the ratio of the output force to the input force, and it can be calculated using the distances from the fulcrum to where the forces are applied.

Types of levers

Levers can be grouped into three types based on where the fulcrum (the pivot point), the effort (the force you apply), and the load (the object being moved) are placed.

• Class I – The fulcrum is between the effort and the load. Examples include a seesaw, a crowbar, and a pair of scissors.
• Class II – The load is between the effort and the fulcrum. Examples include a wheelbarrow and a nutcracker.
• Class III – The effort is between the load and the fulcrum. Examples include a hoe and a pair of tweezers.

Compound lever

Main article: Compound lever

A compound lever is made of several levers working together one after another. The force from one lever becomes the push for the next lever, letting the force move from one lever to another. Some everyday examples of compound levers are scales, nail clippers, and piano keys.

The malleus, incus, and stapes are tiny bones in the middle ear. They are connected like compound levers and help carry sound waves from the eardrum to the oval window of the cochlea.

Law of the lever

See also: Mechanical advantage § Lever

A lever is a bar that moves around a fixed point called a fulcrum. When you push on one end of the lever, the other end moves. The farther you push from the fulcrum, the less force you need to use. This is because points farther from the fulcrum move faster.

This idea is called the law of the lever. It was explained by Archimedes. It shows that if you push farther from the fulcrum, the lever makes your push stronger. If you push closer to the fulcrum, your push becomes weaker. This helps us understand how levers give us an advantage when we use them.

The use of how fast something moves in studying levers helps explain how they work.

Virtual work and the law of the lever

A lever is like a stiff bar that turns around a fixed point called a fulcrum. You can push down at one end, and this makes the other end move up. This helps you lift heavy things more easily.

The lever can make a small force bigger if you push farther from the fulcrum. If you push closer to the fulcrum, the other end moves farther but with less force. This is how levers give us an advantage when we need to lift or move things.