What is Simple Machine?- Definition, Types and Examples

A simple machine is any of several devices with few or no moving parts that are used to modify motion and the magnitude of a force in order to perform work.

They are the simplest mechanisms known that can use leverage (or mechanical advantage) to increase force. The simple machines are the inclined plane, lever, wedge, wheel and axle, pulley, and screw.

What is a machine?

To do anything at all—to lift a box, to push a car, to get out of bed, to jump in the air, to brush your teeth—you need to use a pushing or pulling action called a force. If you go around telling people you’re strong, what you really mean is that your body can apply a lot of force.

You may have watched incredibly strong people on TV pulling trucks or trains with their bare hands, but there’s a limit to what even the most muscle-bound human body can do. Simple machines let us go beyond that limit. Simple machines can make us all strong!

When you hear the word “machine”, you probably think of something like a bulldozer or a steam locomotive. But in science, a machine is anything that makes a force bigger. So a hammer is a machine.

A knife and fork are a pair of machines. And even an egg whisk is a machine. All these machines have one thing in common: when you apply a force to them, they increase its size and apply a greater force somewhere else.

When you pound a nail with a hammer, the handle increases the force you apply. And because the head of the hammer is bigger than the head of the nail, the force you apply is exerted over a smaller area with much greater pressure—and the nail easily enters the wood.

Try pushing in a nail with your finger and you’ll appreciate the advantage a hammer gives you.

What Is a Simple Machine?

A mechanical device that changes the direction or magnitude of a force is known as a simple machine. In general terms, they are defined as simple mechanisms that use leverage or mechanical advantage to multiply force.

Simple machines have few or no moving parts to modify motion and force. Let us learn more about the six simple machines in the following few sections.

Six Simple Machines

The simple machines are the:

• Inclined Plane: Lifts items by advancing up a slope.
• Lever: A device that pivots around to change the mechanical advantage.
• Axle and wheels: A Tool used to lessen friction.
• Wedge: An object that pushes objects apart.
• Screw: A tool used to raise or hold objects together.
• Pulley: Alters the force’s direction.

The Inclined Plane

An inclined plane consists of a sloping surface; it is used for raising heavy bodies. The plane offers a mechanical advantage in that the force required to move an object up the incline is less than the weight being raised (discounting friction).

The steeper the slope, or incline, the more nearly the required force approaches the actual weight.

Expressed mathematically, the force F required to move a block D up an inclined plane without friction is equal to its weight W times the sine of the angle the inclined plane makes with the horizontal (θ).

The equation is F = W sin θ.

The principle of the inclined plane is used widely—for example, in ramps and switchback roads, where a small force acting for a distance along a slope can do a large amount of work.

Examples: Ramp, slide, sloping road, and funnel

The lever

A lever is the simplest machine of all, it’s just a long bar that helps you exert a bigger force when you turn it.

When you sit on a see-saw, you’ve probably figured out that you need to sit further from the balance point (known as the pivot point or fulcrum) if the person at the opposite end is heavier than you.

The further away from the fulcrum you sit, the more you can multiply the force of your weight. If you sit a long way from the fulcrum, you can even lift a much heavier person sitting at the other end—providing they sit very close to the fulcrum on their side.

The force you apply with your weight is called the effort. Thanks to the fulcrum, it produces a bigger force to lift the load (the weight of the other person).

The words “effort” and “load” can be very confusing, so we’ve avoided using them in this article. The important thing to remember about levers is that the force you produce is bigger than the force you apply.

With a long lever, you can exert a lot of leverage. When you use an axe or a wrench, the long handle helps to magnify the force you can apply. The longer the handle, the more leverage you get.

So a long-handled wrench is always easier to use than a short-handled one. And if you can’t budge a nut or bolt with a short wrench, try one with a longer handle.

Examples: Seesaw, crowbar, scissors, and wheelbarrow

The Axle and Wheel

The axle and wheel are machines simple that help reduces the friction required to move an object, making it much easier to transfer. It is important to manage the force of friction when an object is moved to get it rolling. And once an object moves, the force acting on it is opposed by the force of friction.

It is made simpler by the wheel and axle, which lessens the friction that occurs when moving an object. The wheel rolls over the surface with as little friction as possible while spinning around an axle, which is effectively a rod that passes through the wheel and allows it to turn. 

Consider pushing a 9,000-kilogram (around 10-ton) concrete block. Wouldn’t rolling it along with logs under the stone be simpler?

Some of the most frequent examples of axles and wheels are cars, office chairs, motorbikes, shopping carts, wheelbarrows, roller skates, and hand trucks.

Examples: Screwdriver, potter’s wheel, merry-go-round, and windmill

The pulley

A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. Pulleys are used singly or in combination to transmit energy and motion.

Put two or more wheels together and loop a rope around them several times and you create a powerful lifting machine called a pulley. Each time the rope wraps around the wheels, you create more lifting power or mechanical advantage.

If there are four wheels and the rope wraps around them, the pulley works as though four ropes are supporting the load. So you can lift four times as much, although the catch is that you have to pull the rope four times further. Read more in our pulleys article.

Examples: Pulleys can be found in a flagpole, construction crane, water well, and elevator.

The wedge

A wedge is an object that tapers to a thin edge. Pushing the wedge in one direction creates a force in a sideways direction. It is usually made of metal or wood and is used for splitting, lifting, or tightening, as in securing a hammer head onto its handle.

The wedge was used in prehistoric times to split logs and rocks; an ax is also a wedge, as are the teeth on a saw. In terms of its mechanical function, the screw may be thought of as a wedge wrapped around a cylinder.

The head of an axe is a wedge working differently. An axe forces wood apart in two ways. The handle works like a lever, magnifying the force you apply.

The wedge-shaped blade concentrates the force over a smaller area, increasing the pressure on the wood and splitting it apart. The blade of a knife works the same way.

Examples: Knife, axe, scalpel, and shovel

The screw

A screw bites into wood when you turn it around. You often read science books that say a screw is “like a ramp wrapped around in a circle”, which is pretty confusing and hard to understand.

But imagine you’re an ant and you want to climb from the bottom of a screw to the top. If you climb vertically up the outside, you go a relatively short distance but it takes an awful lot of climbing force.

If you walk up the screw thread, winding around and around, you’re really walking up a kind of spiral staircase—a ramp wrapped around in a circle. Yes, you walk much further, but it’s a whole lot easier.

There’s another good thing about a screw too: because the head is bigger than the shaft beneath it, a screw works like a wheel (or lever), each time you turn the head, the sharpened point beneath bites into the wood with greater force. The tapering (cone-shaped) design makes it easier to drive in the screw.

Examples: Bottle cap, corkscrew, car jack, and light bulb

Is there a catch?

Lifting, cutting, chopping, moving, bending—machines like the ones we’ve explored up above make it easier to do all kinds of things by making forces bigger than you can normally create with your own body.

At first sight, that sounds like it might open up the way to designing a machine that can give us something for nothing—maybe one that can make energy out of thin air, or a perpetual motion machine that runs forever.

In practice, the laws of physics are strict and if you make life easier for yourself in one way, you always make it harder in another to compensate.

That’s the scientist’s way of saying “there’s no such thing as a free lunch,” and, in physics, it goes by the name of the law of conservation of energy (simply put: we can’t make energy appear magically out of nowhere).

So whenever you have a machine that gives you more force, it doesn’t give you extra energy you didn’t have before.

With a pulley, for example, ropes and wheels give you much more lifting force, but you have to heave them much further, so you use exactly the same amount of energy as you would have done before.

You just use it more slowly, with less effort, so the lifting feels easier. In the same way, you can use a see-saw to lift a much heavier friend by sitting further from the balancing point than they are, but you have to move your legs much further to compensate.

You get extra force, but no extra energy—and that’s the catch.