Simple Machines

Simple Machines

A simple machine is a mechanical device that changes the direction or magnitude of a force.

Six Simple Machines

• Lever

• Wheel and Axle

• Inclined Plane

• Wedge

• Screw

• Pulley

Lever

A lever is a straight or curved rigid bar that is free to turn about a fixed point.

All levers have three location of interest:

• Fulcrum or Fixed Point

• Point of Effort where work is done on the lever

• Load which is being moved

Classes of Lever

• Class 1 Lever

• Class 2 Lever

• Class 3 Lever

Class 1 Lever

has fulcrum located between effort and load. Class 1 lever includes crowbar, scissors, and pliers.

Class 2 Lever

has the load between the effort and load. The effort and resistance move in the same directions. Examples of class 2 levers are wheel barrows, bottle opener, and nutcracker.

Class 3 Lever

has the effort between the load and the fulcrum. Effort and resistance move in the same direction. Fishing rod, tweezer, and tongs are examples of class 3 levers.

Pulley

A pulley is a grooved wheel that turns around and axle which is held in place by mounting bracket.

Three Kinds of Pulley

• Fixed Pulley

• Movable Pulley

• Compound Pulley

Fixed Pulley

has the axle fixed on a surface and therefore does not move. Its fulcrum is at the center of the axle with load and effort on either side. It does not increase the magnitude, speed, or distance of the force. Fixed pulleys are used in flagpoles and clotheslines.

Movable Pulley

moves along the rope or wire. The fulcrum is at the edge of the wheel with the load at the middle of the axle and the effort at one end of the rope. It increases the magnitude of the force but decreases its distance. Esamples of movable pulleys are ziplines, weight machines, and elevator cables.

Compound Pulley

is made up of a combination of two or more fixed and movable pulleys. Compound pulleys are used in ships and billboards.

Inclined Plane

An inclined plane is a plane tilted at an angle, with one end higher than the other.

Screw

A screw is actually a spiral inclined plane. It is composed of a cylindrical body with a spiral ridge called thread. The treads surround the cylinder from the tip to the head. A screw increases the force but a longer distance.

Wheel and Axle

The wheel and axle is a machine that has a small disk or shaft called an axle that is attached to a wheel.

Wedge

A wedge is an inclined plane or two inclined planes that meet each other to form a sharp edge.