Simple machine

Six Mechanical Powers

BOLT SCREW UBT 199

Kinematics of Machinery - Figure 21

Simple machines are basic mechanical devices for applying a force and doing work. More complex machines are made up of a combination of these simple machines. The traditional list of simple machines is made up of the lever, wheel and axle, pulley, inclined plane, wedge, and the screw. These machines use mechanical advantage to multiply force, making it easier to perform tasks that would otherwise require a much greater amount of effort.

Overview

Simple machines have been known and used since ancient times. The physics behind these devices was first formalized by scientists such as Archimedes in the 3rd century BC. The concept of mechanical advantage, which is the ratio of output force to input force, is key to understanding how simple machines work. By applying a small input force over a greater distance, these machines allow for the output force to be magnified, making it easier to lift heavy objects, cut materials, or hold objects together.

Types of Simple Machines

Lever

A lever is a rigid bar that pivots around a fixed point called the fulcrum. The lever amplifies an input force to lift or move loads. Levers are classified into three types based on the relative positions of the fulcrum, effort, and load.

Wheel and Axle

The wheel and axle consist of a large diameter wheel attached to a smaller diameter axle. When force is applied to the wheel or axle, it reduces the effort needed to move objects over a distance. This machine is often used in transportation and lifting devices.

Pulley

A pulley consists of a wheel on an axle or shaft that is designed to support movement and change of direction of a taut cable or belt. Pulleys are used singly or in combination to transmit energy and motion. Pulleys can also provide a mechanical advantage, allowing heavy objects to be lifted more easily.

Inclined Plane

An inclined plane is a flat surface tilted at an angle to the horizontal. It allows for heavy objects to be lifted by pushing or rolling them up the slope, requiring less effort than lifting them vertically.

Wedge

A wedge is a device that is thick at one end and tapers to a thin edge at the other. It converts force applied to its blunt end into forces perpendicular to its inclined surfaces, allowing it to split materials apart or secure them together.

Screw

A screw is an inclined plane wrapped around a cylinder or cone. Turning the screw converts rotational force into linear motion and force, allowing it to fasten materials together or lift objects.

Applications

Simple machines are found in many everyday tools and machines, from scissors (lever and wedge) and door knobs (wheel and axle) to car jacks (screw) and ramps (inclined plane). Understanding these basic mechanical principles has allowed humans to invent a vast array of more complex machines and tools, significantly impacting technological advancement and efficiency in various industries.

See Also

• Mechanical advantage
• Physics
• History of science
• Engineering

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