Simple Machines — 6 Types, Mechanical Advantage & Examples

Simple machines are basic devices that change the size or direction of a force. The six classical types are the lever, wheel and axle, pulley, inclined plane, wedge, and screw. They do not create energy. In the ideal case, they trade force for distance.

If you remember one idea, remember this: less input force usually means more input distance. Real machines also lose some energy to friction, so they perform worse than the ideal model.

What are the 6 simple machines?

Lever

A lever is a rigid bar that rotates around a pivot called a fulcrum. Crowbars, seesaws, and bottle openers are common examples.

Wheel and axle

A wheel and axle is a large radius attached to a smaller radius so they turn together. A doorknob is a familiar example: turning the larger knob helps rotate the smaller spindle.

Pulley

A pulley uses a grooved wheel and rope or cable. A fixed pulley mainly changes the direction of the force. A movable pulley or pulley system can also reduce the input force needed.

Inclined plane

An inclined plane is a ramp. Instead of lifting an object straight up, you move it along a slope, which can reduce the required force if you accept a longer path.

Wedge

A wedge is like a moving inclined plane. Axes, knives, and chisels use a wedge shape to turn an input force into forces that push material apart.

Screw

A screw is an inclined plane wrapped around a cylinder. Turning it converts rotational motion into forward motion, which is why screws can fasten materials tightly or lift loads in devices such as screw jacks.

Mechanical advantage in simple machines

Mechanical advantage compares output force to input force:

$$\text{MA} = \frac{\text{output force}}{\text{input force}}$$

If $\text{MA} > 1$, the machine lets a smaller input force move a larger load. That does not mean the machine creates extra work. In an ideal machine, the gain in force is balanced by a loss in distance.

You can say the tradeoff this way:

• less force usually means more distance
• more force usually means less distance

That tradeoff is the main idea behind simple machines.

Worked example: a lever

Suppose a lever lifts a load of $200\ \mathrm{N}$. The effort arm is $1.2\ \mathrm{m}$ long, and the load arm is $0.30\ \mathrm{m}$ long.

If we treat the lever as ideal and ignore the weight of the lever itself, torque balance gives

$$F_{\text{in}} d_{\text{in}} = F_{\text{out}} d_{\text{out}}$$

So

$$F_{\text{in}} (1.2) = 200(0.30)$$ $$F_{\text{in}} = \frac{200 \cdot 0.30}{1.2} = 50\ \mathrm{N}$$

So an input force of $50\ \mathrm{N}$ can balance a $200\ \mathrm{N}$ load in this ideal setup. The longer effort arm is what gives the lever its advantage.

The mechanical advantage here is

$$\text{MA} = \frac{200}{50} = 4$$

But there is a condition attached: your end of the lever must move farther than the load end. The machine reduces force by trading for distance.

Common mistakes with simple machines

Thinking a simple machine reduces total work in every case

In an ideal model, a simple machine redistributes force and distance. In a real machine, friction usually means you actually do more input work than the useful output work.

Using ideal mechanical advantage without saying it is ideal

Relations based only on geometry work cleanly only under stated conditions. Real pulleys, screws, and ramps lose energy to friction, so actual performance is lower than the ideal prediction.

Assuming every simple machine always multiplies force

A machine can also be used mainly to change direction or speed. For example, a fixed pulley is often valuable because it lets you pull downward instead of lifting upward directly.

Where simple machines are used

Simple machines appear in hand tools, construction equipment, lifting systems, fasteners, and many everyday objects. They matter because more complex machines are often built from these same basic ideas.

If you can spot the force-distance tradeoff in a lever, pulley, or ramp, you already understand the core of the topic.

Try a similar problem

Take a ramp that is $4\ \mathrm{m}$ long and raises a box by $1\ \mathrm{m}$. Ignoring friction, ask how the ramp trades force for distance compared with lifting the box straight up. Solving that version helps you see the same idea in a new setting.