Simple Machines

A simple machine is a tool with very few moving parts that makes work easier. It does not give you free energy — it lets you trade a long, gentle effort for a short, hard one, or the other way around. Six classic simple machines are hiding in everyday objects all around you.

The Six Simple Machines

• Lever — a stiff bar that turns around a fixed point called a fulcrum.
• Pulley — a wheel with a rope or chain that changes the direction of a pulling force.
• Wheel and axle — a wheel attached to a rod so they spin together.
• Inclined plane — a flat, slanted surface that you push or pull a load along.
• Wedge — two inclined planes back-to-back, used to split or push objects apart.
• Screw — an inclined plane wrapped around a post; it pulls objects together as it turns.

How They Make Work Easier

Imagine lifting a heavy box straight up. It is hard, but the distance is short. Now picture pushing the same box up a long ramp. You do not have to push as hard, but you have to push for longer. That trade — less effort over more distance — is what most simple machines give you. We call it mechanical advantage.

• A lever lets a small effort lift a big load when the load sits close to the fulcrum.
• A pulley lets you pull DOWN to lift something UP, which is much easier for our bodies.
• A wheel and axle turns a small twist of the axle into a long roll of the wheel.
• A ramp (inclined plane) trades distance for effort — long ramp, easy push.

Spotting Simple Machines Around You

• Seesaws, scissors, and bottle openers are all levers.
• Flagpole ropes and window blinds use pulleys.
• Bicycle wheels, doorknobs, and steering wheels use a wheel and axle.
• Wheelchair ramps, slides, and mountain roads are inclined planes.
• Axes, knives, and the tip of a nail are wedges.
• Jar lids, light bulb bases, and bolts use screws.