Category Science

What is a plant?

If someone asked you to name a plant, you might say, “a tree”. You’d probably think of many other green and leafy living things, too. But not all plants are green and leafy. Most are, but not all.

So what makes a plant a plant?

Plants usually spend their whole lives rooted to one place. They can’t move around like animals. Most plants produce seeds to make new plants.

Plants also have special kinds of cells. Plant cells have tough, thick walls made of cellulose. And most plants contain a special substance called chlorophyll. Plants use chlorophyll to make their own food with the help of water, air, and sunlight. Animals have no chlorophyll.

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What Is a Living Thing?

Do you know the difference between a living thing and a nonliving thing? You are a living thing. And so are puppies, trees, and mushrooms. Bicycles, rocks, shoes, and tennis balls are nonliving things.

How do you tell living things from nonliving things? All living things have certain features in common. Almost all living things must have food, water, and air. And they are made up of tiny units called cells. Living things also reproduce, which means they can make new living things just like themselves.

The many, many types of living things are also different from one another in important ways. Scientists separate all living things into large groups called kingdoms. Each kingdom is made up of living things that are similar to one another. Each kingdom is different from the other kingdoms.

Most scientists say there are five main kingdoms. Animals make up one of the kingdoms. Most animals move around and get their food by eating other living things. Plants make up another kingdom. The plant kingdom is important to the other kingdoms because plants create the food that most other living things need. The other kingdoms include organisms such as fungi and algae.

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How does television work?

Did you know that the pictures on TV are a jumble of red, green, and blue dots? When you sit across the room, the dots blend into the images you see.

At the television station, a camera records the picture and sound from the scene you are watching. Mirrors in the camera split light from the scene into red, green, and blue. A tube in the camera changes the light to radio signals. The television station broadcasts the programme to your home.

TV antenna, cable, or satellite dish A receives many broadcast signals at once. The television tuner is used to select the signal for the TV channel you want to see. The tuner passes this signal to the amplifier. The amplifier separates the sound from the pictures.

The sound goes to the speakers. The picture signal is sent to a decoder. The decoder sends the signal to the electron guns. There is one gun for each colour red, blue, and green. The electron guns zip across the screen in weak or strong bursts of light. These bursts form the picture you see on the screen.

 

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How does a radio work?

Radio signals are heard almost everywhere. But how does a radio work? The radio transmitter (where the sounds come from) changes sound waves into electrical signals. It sends them through the air as radio waves. The radio waves that leave the transmitter have different frequencies for each station. Frequencies are the number of times the waves vibrate per second.

You tune your radio by choosing a number on the controls. Each number represents a frequency. So if you always tune in the same frequency, you always pick up the same station.

When you tune in a station, signals are picked up by the radio. These signals are sent to an electromagnet in the radio speaker. The electromagnet makes a cone on the speaker vibrate. These vibrations are the sounds you hear on your radio. They sound exactly like the sounds made at the transmitter-voices, music, or even the squeak of a mouse.

An Italian inventor, Guglielmo Marconi, realized that coded messages could be sent over long distances without using wires. Because the transmitter and receivers did not need wires, the process was called wireless telegraphy. This discovery led to present-day radio.

 

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Who designs cars?

Many people work M together to design a new car.

First, drawings are made with a computer. This is called computer aided design, or CAD. Computers are used to create, test, and change the plans. This saves time and money. Next, artists may make a clay model of the car. The clay is coated with shiny film. It looks like a real car.

Other artists create the inside of the car. They design the seats. They decide where the controls will be. They plan everything from turning signals and seat belts to airbags and drink holders.

Finally, a fibreglass model of the car is built. It has real tyres, glass windows, and trim. This final model looks exactly like the new car will look.

Product engineers plan how each part of the car will be made. They use a computer that traces every line and curve on the final model. Factories make the parts and a completed car is made and tested.

Next, parts are shipped to several factories to be assembled. Each worker in the assembly line adds a different part. At the end, a complete car rolls off the line.

 

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How do rocket engines work?

A jet fighter plane is very powerful, but it can’t fly into space. Why not? There is no oxygen in space to power the engine!

All fuel needs oxygen to burn, but a rocket engine does not need air It carries its own supply of oxygen.

Planes get oxygen from the air. But rockets get oxygen from a substance called an oxidizer. Some space rockets use solid fuels with solid oxidizers. They work in the same way as a fireworks rocket-a fireworks rocket as big as a 10 storey building!

Other space rockets use liquid fuels and oxidizers, so that the engines can be switched on or off.

The liquids are pumped into a special part of the rocket called the combustion chamber. Here the fuel burns violently to thrust the rocket upwards further away from the earth.

The Saturn V moon rocket burned over 2,120,000 litres of fuel during its first 105 seconds of flight. This pushed the rocket off the launching pad with a huge amount of force. If you want to get to the moon and back again you have to think big-really big!

Fireworks rockets are displayed at many festivals. Fuel in a fireworks rocket burns like fuel in a rocket engine. In fireworks, the fuel is charcoal and sulphur. The oxygen is supplied by a solid oxidizer called saltpetre. This mixture burns very hot. The gases given off push in all directions against the inside of the rocket. The gases that push against the top of the rocket make the rocket go! The fireworks rocket has a stick that keeps it pointed in the right direction. 

 

Picture Credit : Google