What are simple machines?

They are inventions that that people thought of thousands of years ago

to make their lives easier.

Did you know that we use those same simple machines every day in our modern world?

Let's look at some of our modern inventions

that are actually simple machines!

The Lever

There are many modern inventions that are levers.

A hammer is a lever that you use to pull out nails.

A bottle opener is a lever, too.

You use it to take off bottle caps.

When you ride on a seesaw in the playground,  you're using a lever.

The board rests on a point in the middle.

When you push down on  one end f the board, the other end goes up.

The Ramp

A ramp is a flat surface that has one high end and one low end,

making it easier for us to climb.

Do you know that you use a ramp at school or at home every day?

You use the stairs!

People in wheelchairs and cars also use ramps.

Of course, there are many ramps  in nature.

They are called hills and mountains!

The Wedge

A wedge is like two ramps put together, so that one edge is sharp.

You might ask, "When would I need a wedge?"

If you enjoy eating, you need one almost every day!

A knife and a fork are both wedges, which cut into food.

So is an axe, which people use for chopping wood.

We use this sharp edge to push things apart.

The Screw

A screw is a ramp that winds around and around in a circle.

When you turn the screw, it moves and pushes against something else.

If you use light bulbs, you are using a  screw to put them tightly into lamps.

Jar lids are also screws.

Without the screw, it would be  very difficult to hold things together tightly.

The Wheel and Axle

A wheel and axle is a very simple machine,

but important for many modern inventions.

An axle goes into the middle of a wheel, making it easy to turn.

We use the wheel and axle on many of  our vehicles: cars, trucks, and bicycles.

Can you imagine a world without clocks, computers, or even doorknobs?

They all use the wheel and axle.