# Simple Machines

## A simple machine is a device that changes the direction of a force or augments a force; simple machines fall into six categories.

#### Key Points

• The six classifications of simple machines were established by the renaissance scientist; they are as follows: lever, wheel and axle, pulley, inclined plane, wedge and screw.

• Simple machines can be joined with other devices to create a more complicated machine. These building blocks are used to explain how machines work.

• The force output by the machine can not exceed the force that was put into the machine.

#### Terms

• A mechanical or electrical device that performs or assists in the performance of human tasks, whether physical or computational, laborious or for entertainment.

• A force compounded by means of a lever rotating around a pivot; see torque.

#### Figures

1. ##### Lever

The amount of force produced by a machine can not be greater than the amount of force put into it.

2. ##### Examples of Simple Machines

Both of these machines use the concept of levers.

3. ##### Simple Machines

Table of simple mechanisms, from Chambers' Cyclopedia, 1728.[1] Simple machines provide a "vocabulary" for understanding more complex machines.

4. ##### Simple Machines, Pulleys; Forces, Distances and MA

Describes the following terms as they relate to simple machine; input force, output force, input distance, output distance, mechanical advantage.

## Simple Machines

A simple machine is a device that changes the direction or magnitude of a force. They can be described as the simplest mechanisms that provide leverage Figure 4. Usually the term simple machine is referring to one of the six classical simple machines, defined by Renaissance scientists.

Simple machines are devices used to multiply or augment a force that we apply—often at the expense of a distance through which we apply the force. Some common examples include:

• Lever
• Wheel and Axle
• Pulley
• Inclined Plane
• Wedge
• Screw

When a device with a specific movement, called a mechanism, is joined with others to form a machine, these machines can be broken down into elementary movements. For example, a bicycle is a mechanism made up of wheels, levers, and pulleys. Figure 3 shows a table of various simple machines.

### Mechanics

A simple machine has an applied force that works against a load force. If there are no friction losses, the work done on the load is equal to the work done by the applied force. This allows an increase in the output force at the cost of a proportional decrease in distance moved by the load. The ratio of the output force to the input force is the mechanical advantage of the machine. If the machine does not absorb energy, its mechanical advantage can be calculated from the machines geometry. The mechanical advantage of a lever, shown in Figure 1, is equal to the ratio of its level arms. Simple machines which do not experience friction loss is called an ideal machine. For these ideal machines, the power (rate of energy) in equals the power out: $P_{in}=P_{out}$.

### Further Examples

Wheelbarrows and shovels are also examples of simple machines (these utilize levers). They use only three forces: the input force, output force, and force on the pivot. In the case of wheelbarrows, the output force is between the pivot (wheel's axle) and the input force. In the shovel, the input force is between the pivot and the load (refer to Figure 2).

#### Key Term Glossary

energy
A quantity that denotes the ability to do work and is measured in a unit dimensioned in mass × distance²/time² (ML²/T²) or the equivalent.
##### Appears in these related concepts:
force
A physical quantity that denotes ability to push, pull, twist or accelerate a body which is measured in a unit dimensioned in mass × distance/time² (ML/T²): SI: newton (N); CGS: dyne (dyn)
##### Appears in these related concepts:
Force
A force is any influence that causes an object to undergo a certain change, either concerning its movement, direction or geometrical construction.
##### Appears in these related concepts:
friction
A force that resists the relative motion or tendency to such motion of two bodies in contact.
##### Appears in these related concepts:
leverage
A force compounded by means of a lever rotating around a pivot; see torque.
##### Appears in this related concept:
machine
A mechanical or electrical device that performs or assists in the performance of human tasks, whether physical or computational, laborious or for entertainment.
##### Appears in these related concepts:
magnitude
A number assigned to a vector indicating its length.
##### Appears in these related concepts:
plane
A level or flat surface.
##### Appears in these related concepts:
power
A measure of the rate of doing work or transferring energy.
##### Appears in these related concepts:
work
A measure of energy expended in moving an object; most commonly, force times displacement. No work is done if the object does not move.