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Levers are Simple Machines

by Ron Kurtus (revised 26 July 2016)

A lever is a simple machine that allows you to gain a mechanical advantage in moving an object or in applying a force to an object. It is considered a "pure" simple machine because friction is usually so small that it is not considered a factor to overcome, as in other simple machines.

A lever consists of a rigid bar or beam that is allowed to rotate or pivot about a fulcrum. An applied force is then used to move a 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:

This lesson will answer those questions. Useful tool: Units Conversion



Parts of a lever

A typical lever consists of a solid board or rod that can pivot about a point or fulcrum. Since humans usually provide energy to levers, "effort" and "load" are often used instead of input and output.

An input force or effort is applied, resulting in moving or applying an output force to a load.

The distance from the applied force or effort force to the fulcrum is called the effort or input arm and the distance from the load to the fulcrum is called the load or output arm.

Parts of a Lever

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.

Lever configurations

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

(See Three Lever Classes for more information.)

Class 1

A class 1 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. This is the most typical lever configuration.

Class 1 lever

Class 1 lever

Class 2

A class 2 lever has the load 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 class 2 lever.

Class 2 lever

Class 2 lever

Class 3

A class 3 lever has the effort between the load and the fulcrum. Both the effort and load are in the same direction. Because of the configuration, the fulcrum must prevent the lever beam from moving upward or downward. Often a bearing is used to allow the beam to pivot.

(See Three Lever Classes for details.)

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 class 3 lever. The result is a force mechanical advantage less than 1.

Class 3 lever

Class 3 lever

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.

(See Mechanical Advantage for more information.)

Increase force

You can increase the applied force in order to lift heavier loads.

(See Increasing Force with a Lever for more information.)

Increase distance moved

You can increase the applied force in order to lift heavier loads.

(See Increasing Distance Moved with a Lever for more information.)

Increase speed

You can increase the speed that the load moves with Class 1 or Class 3 levers.

(See Increasing Speed with a Lever for more information.)

Summary

A lever is a simple machine that allows you to gain a mechanical advantage. It consists of a consists of a rigid bar or beam that is allowed to rotate or pivot about a fulcrum, along with an applied force and load. The three types or classes of levers, depend on where the fulcrum and applied force is located.

Uses for a lever are that you can move a heavy object using less force than the weight of the object, propel an object faster by applying a force at a slower speed, or move an object further than the distance you apply to the lever.


Leveraging gives you an advantage


Resources and references

Ron Kurtus' Credentials

Websites

Lever - Wikipedia

Levers - TechnologyStudent.com

The Lever - Ohio University lessons for Middle School students

Machines Resources

Books

Top-rated books on Simple Machines


Questions and comments

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.


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