Read About How Machines Work

Every time you open a door, ride a bike, or cut with scissors, you are using a machine. Machines are tools that make work easier by changing the direction or size of a force.

What is a machine?

• A machine is a device that uses force (a push or pull) to do work.
• Machines do not reduce the amount of work — they make it easier to do by spreading force over a longer distance or changing its direction.
• There are two types: simple machines (basic tools with few or no moving parts) and complex machines (made by combining two or more simple machines).

The six simple machines

• Lever — a rigid bar that pivots on a fulcrum. Example: a seesaw, a bottle opener.
• Wheel and axle — a wheel attached to a rod. Example: a doorknob, a car wheel.
• Pulley — a wheel with a groove for a rope. Example: a flagpole, a blinds cord.
• Inclined plane — a flat, sloping surface. Example: a ramp, a slide.
• Wedge — two inclined planes joined to a sharp edge. Example: a knife, an axe.
• Screw — an inclined plane wrapped around a cylinder. Example: a bolt, a jar lid.

Complex machines

• A bicycle uses a wheel and axle plus a lever (handlebars and pedals) and a screw (the bolts holding it together).
• A pair of scissors is two levers joined at a pivot, with wedge-shaped blades.