Understanding Lever

Lever is a Simple Machine

object or in applying a force to an object. It is considered a "pure" simple machine because friction is not a factor to overcome, as in other simple machines.

A lever consists of a fulcrum, applied force and load. There are three common types or classes of levers, depending on where the fulcrum and applied force is located. The mechanical advantage is that you can move a heavy object using less force than the weight of the object, you can propel an object faster by applying a force at a slower speed, or you can move an object further than the distance you apply to the lever.

Questions you may have include:

• What are the parts of a lever?
• What are the three lever classes?
• What are the uses for a lever?

Parts of a lever

A typical lever consists of a solid board or rod that can pivot about a point or fulcrum. A force or effort is applied, resulting in moving or applying force to a load. The distance from the applied force or effort force to the fulcrum is called the effort arm and the distance from the load to the fulcrum is called the load arm

Parts of a Lever

Since there is typically a very small amount of friction at the fulcrum, overcoming friction is not a factor in a lever as it might be in another simple machine like a ramp or wedge. Thus, we consider a lever a pure simple machine.

Three lever classes

There are three types or classes of levers, according to where the load and effort are located with respect to the fulcrum

1st Class

A 1st class lever has the fulcrum placed between the effort and load. The movement of the load is in the opposite direction of the movement of the effort. Note that the length of the effort arm can be greater than, equal to or less than the length of the load arm in a 1st class lever

1st class lever

Examples of 1st class levers include:

• Teeter-totter
• Oars on a boat
• Catapult
• Shoehorn
• Scissors
• Pair of pliers

Double 1st lever

A scissors and a pair of pliers are considered double 1st levers.

A pair of pliers is a double 1st lever

2nd Class 

A 2nd class  lever has the load in between the effort and the fulcrum. In this type of lever, the movement of the load is in the same direction as that of the effort. Note that the length of the effort arm goes all the way to the fulcrum and is always greater than the length of the load arm in a  2nd class  lever.

2nd class lever

Examples of  2nd class  levers include:

• Wheelbarrow
• Crowbar
• Nut cracker

3rd Class 

A 3rd class  lever has the effort in between the load and the fulcrum. Both the effort and load are in the same direction. Note that the length of the load arm goes all the way to the fulcrum and is always greater than the length of the effort arm in a  3rd class  lever.

3rd class  lever

Examples of  3rd class   levers include:

• Tweezers
• Stapler
• Mousetrap
• Broom
• Hockey stick

Uses for a lever

The reason for a lever is that you can use it for a mechanical advantage in lifting heavy loads, moving things a greater distance or increasing the speed of an object.