# Simple Machines

## What is a Simple Machine?

Simple machines are mechanical devices which are used to change the direction or magnitude of an applied force as per our requirement.

• It is the simplest form of mechanism which uses mechanical advantage to get a multiplied effect of applied force.
• In ancient period, early men have invented six types of simple machines which are now the base of modern machines.

### Compound Machine

A combination of small components working together as a single unit as a machine is known as a compound machine or complex machine. By fundamental nature, each component is a basic simple machine. Thus, simple machines are building blocks of compound machines.

A compound machine or complex machine is made up of a chain of many components. By fundamental nature, each component is a basic simple machine which may be a lever, a screw, a wedge, an inclined plane or a wheel and axle.

Thus, simple machines are the building blocks of a compound machine. Mechanical advantage of a compound machine is the total sum of individual mechanical advantages of each of components.

### Basic Machines

A basic machine is a man-made mechanical device which takes energy in an available form and uses it convert into another form of energy or a desired work.

Therefore, a basic machine can modify a motion or an applied force to perform a desire work.

Basic machines are of two types –

1. Simple machine.
2. Compound machine.

EXAMPLE –

1. When electric current is switched on, an electric motor rotates. Thus, an electric motor receives electrical energy as input and converts it into rotation of its rotor. Thus, we get kinetic energy at output. Therefore, it is a machine.
2. Similarly a bicycle, a clock or a straight rod etc. are examples of machines.

## Types of Simple Machines

Simple machines are of six types –

1. Wedge.
2. Inclined plane.
3. Lever.
4. Pulley.
5. Wheel & Axle.
6. Screw.

### Wedge

A wedge is consists of two oppositely inclined planes attached to form a sharp edge.

• A wedge is used to take advantage of frictional force in a desired direction.
• Wood cutter’s axes is the simplest example of a wedge. Its working is shown in figure.
• Wedge is the oldest invention in ancient period among all of simple machines.
• All present machines are based upon the basic working principle of a wedge.

USE –

1. A wedge is used to cut things. Example – a knife, axes etc.
2. It is used to arrest the accidental movement of round objects. Example – arresting rolling of wheels of standing trucks, rail coaches etc.
3. Wedge is used for fine alignment of heavy machine beds etc.

### Inclined Plane

A sloping or slanting surface or a ramp is called an inclined plane.

An inclined plane is shown in figure.

• It is a simple machine made of a flat inclined surface.
• It is used for lifting a heavy load for small height. In an inclined plane, a smaller input force is applied over a longer distance.

Inclined plane is the second oldest invented simple machine used in ancient period. It was used by the ancient people to move heavy objects to a height.

USE –

1. An inclined plane is used to lift a heavy load easily to a certain height.

### Lever

A lever is a rigid bar or a cylindrical rod which is capable to rotate about a fixed point called fulcrum point.

In ancient period, it was used to move large objects in Egyptian technology. Working of a lever is shown in figure.

USE –

1. A lever is used as a force multiplier. Example – Bottle opener, scissors etc. are simple examples of lever.
2. A lever is used to get large force output by applying a small force input.

### Pulley

A pulley or sheave is a disc like object with a groove on its rim. In this groove, a flexible rope or chain is wrapped for application of pulling force or effort.

A pulley used for lifting water buckets from a well is a common example of simple pulley system.

Working of a pulley system is shown in figure.

USE –

1. A pulley system is used for lifting of heavy loads at considerable large height. Example – Erection and installation of heavy machinery on structural frames, girders etc.
2. It is also used for changing the direction of effort or motion. Example – Pulley used for lifting water buckets from a well.

### Wheel & Axle

A wheel and axle device is made up of a circular frame called wheel disc which is mounted on a cylindrical shaft or rod called axle.

• In this device, two wheel discs are mounted on two ends of an axle.

• Normally input force is applied on the axle. From axle, the force gets transferred to wheel discs.
• In ancient period, wheel and axle was invented in Mesopotamia.

Working of a wheel and axle system is shown in figure.

USE –

1. A wheel and axle assembly is used for easy rolling of loads on surfaces. Example – Wheels of automobiles etc.
2. In ancient period it was used for raising weights or water buckets from wells.

### Screw

A screw is made by wrapping an inclined plane on a circular cylinder.

• It is a circular cylindrical object looks like a nail.
• Screw is the last invention among all simple machines invented by our early men.
• It was first used in Mesopotamia.

Working of a basic screw system is shown in figure.

USE –

1. A screw is used as a fastener. Example – Carpenter Screws, Nuts & bolts etc.
2. It is used for transmission of force and motion. Example – Worm and worm wheels etc.

See numerical problems based on this article.