Category Science

Four wheels, two axles, a box, and a handle. That is all a wagon is. But with a wagon, you can easily carry a couple of friends or even give your dog a ride. When you use a wagon, wheels and axles are helping you. You can see the wheels. They are the round parts that roll over the ground. The axles are the rods that connect each pair of wheels. The wheels and axles turn together.

Putting wheels and axles on something makes it easier to move. It would be hard to pull a wagon without wheels. It would just drag over the ground. But wheels on axles roll along smoothly. Cars, trucks, and buses have wheel-and-axle parts, too.

Every day you are helped by other kinds of wheels – wheels that do not roll. A doorknob is a kind of wheel-and-axle machine. The knob is the wheel! You turn it to make the axle pull back the latch so the door can open.

A pencil sharpener has a wheel and axle, too. The handle is part of a wheel. When you turn the handle, it turns an axle that makes the other parts work.

Picture Credit : Google

Wham! Wham! Wham! It is easy to nail two pieces of wood together. You just knock in nails with a hammer. But fastening two pieces of wood together with a screw is not so easy. The screw has to be turned many times to go into the wood.

A screw has a winding edge called a thread. The thread usually goes from the bottom nearly all the way to the top. When you turn the screw, you wind the thread into the wood.

Turning a screw takes more time than hammering in a nail the same size. But the winding thread of the screw is much longer than the straight sides of the nail. There is more of it to grip and hold the wood. So for some jobs, a screw works better than a nail. It holds things together better than a nail would.

A screw really is an inclined plane that curves around and around. Make a paper screw and see for yourself. Cut a triangle shape as shown from a corner of lightweight card. Mark the square corner with an X.

The long cut edge is an inclined plane. Colour this edge with a crayon or felt-tipped pen. Starting at the straight end, with the X next to the rubber, wind the triangle around a pencil. The coloured edge shows you how the inclined plane winds around the screw to form the threads.

Picture Credit : Google

Be careful! That knife is sharp! Don’t prick yourself with that pin! Working with sharp things means taking special care. But some things have to be sharp to work well. A dull knife or a pin without a point isn’t much help at all.

Sharp things have a special shape that makes work easier. They are really all one kind of machine – a machine called a wedge. The thin, sharp end of a wedge can cut or push into things easily. Then the thicker part of the wedge can push through. Knives, saws, and scissors are wedges for cutting. Pins, nails, and needles are wedges used for pushing into or through things. The point makes it easy for the drawing pin to stick into a notice board, for the nail to push into wood, and for the needle to push through cloth.

Axes and metal wedges are used to push the sharp edge into a log. Then the wider part spreads the wood and makes it split.

Many boats have a wedge-shaped bow, or front end. The bow cuts through the water and makes it easy for the boat to glide along.

Slides and Steps

Is a sloping board without a fulcrum a machine? It is if you use it to do some work. It is a kind of simple machine called an inclined plane. Inclined means sloping, and a plane is a flat surface. So an inclined plane is a flat surface that slopes, like a slide in a playground or a ramp.

An inclined plane makes it easy to move things up and down. When you use an inclined plane, you spread out the amount of work you do. If you lift a heavy box onto a table, you move it only a short distance – straight up. But you are doing all the lifting at once. If you slide the box up an inclined plane, you do the lifting little, by little, so the job is easier.

There are other ways to use inclined planes, too. When you wheel your bike or roll a wheelchair up and down a ramp, you are using an inclined plane.

The kind of inclined plane you use most often may not look like one. A stairway is an inclined plane with steps on it. The steps help keep the plane shorter. Imagine how long the inclined plane would have to be if you flattened out the stairs!

Machines can be any shape and size, but they all have one thing in common: they help people do work. When we think of machines, we usually think of big ones with many parts. These machines do big jobs, such as digging holes, washing clothes, or mowing lawns.

But some machines are small. You cut things out with a small machine – a pair of scissors. You sew with a small machine – a needle. And you tighten a screw with a small machine – a screwdriver. These small machines help you do work, too.

It’s built to last you a lifetime – quite literally. But though the human body is the most amazing tool at your disposal, it often needs a helping hand. Tools made from metal, wood, and plastic work like extensions of your body, making you feel stronger and helping you work faster and more efficiently. In science, tools like this are called simple machines. And although you might think there’s a big difference between a tiny little wrench and a huge great earthmover, exactly the same physics is at work in both.

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!

Picture Credit : Google

How many times can you lift your best friend higher than your head? How many times can your best friend lift you? It doesn’t sound easy, but it is. When you and your friend are on a seesaw, that’s exactly what you are doing.

The seesaw you and your friend are riding is really a kind of machine called a lever. A lever makes pushing and lifting easy, even when things are heavy and hard to move.

The simplest kind of lever is just a straight stick or board and something to rest it on. Suppose you want to move something heavy – a big rock for example. You can push one end of a strong board under the rock. Then you can rest the middle of the board on a log. This is the resting place, or fulcrum. The end of the board near you sticks up. If you push down on the high end of the board, the other end will move up. The heavy rock will move, too.

Archimedes, an ancient Greek scientist, was the first person to describe how levers work. To prove the power of levers, he built a machine that he used to launch a ship all by himself.

When you ride a seesaw, you and your friend take turns using it as a lever. The middle of the seesaw is the fulcrum. Your weight pushes one end down and lifts your friend up. Then your friend’s weight pushes the other end down and lifts you up.

Picture Credit : Google