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A lever reduces the amount of effort required to perform a specific task.

We can break up a lever into 3 sections

In the case of a Seesaw. The person who is at the top is the effort and the bottom person is the load.

This is because the effort must over come the forces on the load.



The closer the load is to the fulcrum, the less energy you need to put into moving the load.

We can put a small amount of force in one end and have a big amount of force on the other end.

But well talk about that further down.

We can break levers up into 3 classes.

The only difference between these classes is the position of the load, fulcrum and effort

Class 1

The fulcrum is placed in between the load and effort.

Effort - Fulcrum - Load

The movement of the Load is in the opposite direction to the effort.

It is the most typical lever configuration.

Seesaws, Scissors, Pliers and Catapults are examples of class 1 levers.

Class 2

The Load and Effort are both on the same side of the fulcrum. As you can see in the animation to the left, the load is in between the effort and fulcrum.

Effort - Load - Fulcrum

Unlike class 1, the effort and load are both moved in the same direction.

Wheelbarrow, crowbar and nut cracker are types of class 2 levers.

Class 3

I this case ,the Effort is in between the fulcrum and load.

Loaf - Effort - Fulcrum

Tweezers, staplers and mousetraps are examples on class 3 levers.

The human body uses the same principles as levers for most of its basic movements.

Observe the forearm to the left. You’ll notice this is a 3rd class lever system.

Increasing Distance or Speed

We can increase the distance and speed that the load travels by altering the position of the Fulcrum.

Essentially, the load arm must be longer than the effort arm.

 Click here to see a trebuchet

Increasing Force

We can increase the Force that the load is moved by altering the position of the Fulcrum.

Essentially, the load arm must be shorter than the effort arm.

(The opposite of increasing distance)

Increasing Force (leg curl)

If you go to the gym and go on the leg curl machine, you can use you knowledge of levers to impress every one around.

The closer the leg support (load) is to you knee joint (fulcrum) them more you should be able to lift, with the same amount of effort.

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