When a cycle is moving at a great speed, will you be able to see the lower and upper spokes of the wheels clearly? Let's find out.

What you need:

A bicycle and a friend to ride it.

What you do:

 • Ask your friend to cycle fast.

• Watch the upper and lower spokes of the wheels.

What you find:

The spokes of the wheels that are below are clearly visible but the upper spokes are a blur. Does it mean that the top of the rolling wheels moves faster than the bottom?

Yes. This happens because while the wheels are rotating on their axle, they are also moving forward along with the axles. At the top, the two motions are in the same direction but at the bottom the rotation is in the reverse direction.

Picture Credit : Google 

When you don’t clean the ceiling fan for some time, do the blades get uniformly dirty or do they get dirty in parts? Let’s find out.

What you do:

  • Ask your mom not to clean the ceiling fan in your room for two to three weeks
  • Observe the blades of the fan at the end of this period.

What you find:

That most of the dirt collects on the leading edges of the blades.

 Why does this happen?

Static electricity develops on the blades of the fan when they are in motion due to friction with the air The static electricity attracts dust particles. As the edges of the blades are the first to come into contact with the surrounding air, more dust collects on them than on the other parts of the blades.

Picture Credit :Google 

What are the different stages of vaccine development?



Nine months into the COVID-19 pandemic, scientists and pharmaceutial companies around the world are racing to develop an effective vaccine against SARS-CoV-2, the coronavirus that causes COVID-19. According to the latest list of the World Health Organization (WHO), at least 200 vaccines are at various stages of development.



According to Russian State media, the first batch of Russia’s vaccine, Sputnik V, entered “civil circulation” on September 24 in capital Moscow. However, its safety and effectiveness is being looked at sceptically because the results of only the phases 1 and 2 of the trials have been published. Earlier, reports emerged that the third stage trials were ongoing in Russia and a few other countries. Phase 3 of clinical trials of the Sputnik V vaccine will begin in India in the coming weeks.



China has about 11 vaccine candidates in various stages of human testing. China has been administering experimental coronavirus vaccines to large numbers of workers deemed to be at high risk of exposure to the virus. They include frontline health workers, public service workers and border officials. A vaccine developed by CanSino Biologists and named Ad5-nCoV was approved for use within the Chinese military as early as June 2020. Four other vaccines are in the final stages of clinical trials. Chinese officials say that the country will be able to roll out a vaccine for public use by November or December. China has promised to provide doses to at least 62 countries.



Among other vaccine contenders that have drawn global attention is the one being developed by the Oxford University in partnership with phaemaceutical company AstraZeneca. Hopes were high when it successfully carried out phases 1 and 2 of the trials. But the final clinical trials had to be briefly put on hold in September after a study participant developed a suspected serious adverse reaction.



COVID-19 vaccines are also being developed by Pfizer and BioNTech in the U.S. and Germany; Johnson and Johnson in the U.S.; Sanofi along with GlaxoSmithKline in the U.K. and Franc; and Novavax in the U.S. Some of these companies have signed deals with multiple countries for trials.



Back home, in India, there are at least eight vaccine candidates under development. The phase 3 clinical trial of ‘Covishield’, being developed by Oxford University and the Serum Institute of India, is underway. Indian candidates, Covaxin, by Bharat Biotech, and ZyCoV-D, by Zydus Cadila, are currently in phase 2 trials.



Experts maintain that even at this speed a vaccine will not be ready before mid-2021.



 



Picture Credit : Google


What happens when you put water on a candle?



Warm the base of a candle and stick it to the bottom of a small bowl. Pour water into the bowl till the water reaches the rim of the candle. Light the candle. It will burn and the flame will form a crater in the candle.



The base of the flame will sink below the surface level of the water, but the water will be prevented from extinguishing the flame by the thin wall of wax that is left standing all around it.



How does the wall form?



The water takes up so much heat that the outer layer of the candle does not reach melting point. As a result, the wax there cannot evaporate and burn. It remains like a wall around the flame.



 



Picture Credit : Google


Before cooking an egg, how do you find out if it is fresh or stale?



Immerse the egg in a bowl of water. If the egg lies horizontally on the bottom of the vessel containing the water the egg is probably fresh; if the egg stands on its pointed end, the egg may be several days old.



What is the basis for testing of freshness of eggs in this way?



Eggs contain tiny pores invisible to the naked eye, through which air can enter or leave the egg. The air in the egg is contained in the air cell situated at the broader end of the egg.



Due to the gradual evaporation of water from the egg after it has been laid, the air cell becomes larger as the days pass. This makes the broader end lighter than the rest of the egg, so if an egg that is several days old is placed in water, the broader side will float upward causing the egg to stand on its pointed end.



 



Picture Credit : Google


What are the great scientific discoveries?



Life is full of problems, and scientists are always trying to find new ways to solve them. There are hundreds of great scientists who have changed our lives for the better,through their discoveries and their inventions. Here are seven of them.



Evolution



Charles Darwin worked out how animals, such as moths and beetles, can change over many generations to become new species. This process is called evolution.



Computers



Ada Lovelace wrote the first published computer program. She also predicted that a computer would be able to make music and images, not just do sums.



Light bulb



Thomas Edison is best known for inventing the first light bulb that could be made in large numbers. He also invented a sound-recorder and a moving-image projector, which helped to start the age of movies.



Gravity



Issac Newton is said to have discvered how gravity works when he saw an apple fall from a tree. He realized that there must be a similar force that keeps the Earth moving around the Sun.



Radioactivity



Marie Curie discovered two substances, called radium and polonium, which give off invisible rays that can pass through materials. She called these rays radioactivity.



Relativity



Albert Einstein’s theories of relativity, along with his ground-breaking E = mc^2 equation, helped scientists to understand the Universe, and how energy, mass, space, and time are all related.



Antibiotics



Alexander Fleming discovered penicillin, which led to the creation of a group of medicines called antibiotics. They kill the bacteria that cause many infections in humans and other animal, and so have saved millions of lives.



 



Picture Credit : Google


What is the human skeleton made of?



Like all vertebrates, humans have a bony skeleton underneath their skin and muscles. It is a framework to hold up the body, help it move, and protect what is inside. The amazing brain makes humans the cleverest of all the animals. That includes you!



Thinking



The brain controls the body, sorting out information from the world around you and sending out instructions. It also stores memories.



Pumping



With each beat, the heart pumps blood around the body, delivering nutrients and oxygen to every part.



Breathing



Lungs bring air into the body through breathing. This air contains oxygen, which is needed to keep the body alive.



Eating



The body needs food to survive. The digestive system breaks food down, keeping the nutrients and getting rid of the waste.



Strong muscles



Muscles are like elastic straps that can stretch or squeeze. Many muscles move the body by pulling on the bones.



Standing tall



Unlike most animals, humans walk upright on two legs. This allows the arms to be used for other activities such as making things.



Body facts




  • Human skeletons contain more than 200 bones. The smallest bone is inside the ear and in only 3 mm (3/25 in) long.

  • The thigh bone is the strongest bone in the body. It is about four times stronger than concrete.

  • A human heart beats more than 100,000 times in a day. That is over 35 million times in a year.

  • In one day, blood travels about 19,000 km (12,000 miles) around the body.



 



Picture Credit : Google


What are Animals?



There are millions of different types of animal on Earth, so scientists have divided them into groups, based on features that they share. For example, is their body covered in fur, feathers, or scales? The amazing imaginary animal shown here combines key parts of animals from six well-known groups.



Insects



All insects have six legs and a pair of feelers on their heads, like this moth. Most of them have wings and can fly.



Reptiles



Reptiles are covered in hard, dry scales, or a shell, like this tortoise. They have either four legs or no legs at all.



Mammals



Mammals have fur or hair on their bodies, and feed their babies milk. Humans are a type of mammal.



Birds



Birds have wings, and they are the only animals that have feathers, which keep them warm and help them to fly.



Fish



All fish live in water and use their tails to help them swim. Their bodies are covered in scales, and they have gills for breathing underwater.



Amphibians



Amphibians live both on land and in water. Most of them have four legs, which they use for walking and swimming.



 



Picture Credit : Google


How is science involved in everyday life?



Science is all around us. From the moment we wake up to the moment we go to bed, almost everything that we do or that happens to us can be explained by science. Here are a few examples of the ways that science helps us to understand what goes on in our daily lives.



Wakey wakey!



Science explains how a cockerel could wake us up in the morning. Sound waves travel through the air from the cockerel’s mouth to our ears.



Light the way



Science explains how flicking a switch turns on our lights, by allowing electricity to flow around an electrical circuit.



Keeping warm



Science explains how our clothes keep us warm. Wool and cotton are poor conductors of heat energy, so they stop our body heat from escaping.



Eat up!



Science explains why we need to eat food every day. Food contains stored energy that we need in order to move, grow, and keep warm.



On the move



Science explains how wecan use a bicycle to travel quickly. The grip of the tyres produces friction between the wheel and the road, which helps to push the bike along.



Sun power



Science explains why a plant grows when we put it on a windowsill. Plants use energy from sunlight to produce food, which gives the plant energy to grow.



Ball games



Science explains why a ball moves when we kick, throw, or hit it. Our arms and legs produce a force that propels the ball forwards.



Time for bed



Science explains why the Moon stays in the sky. The force of gravity from the Earth pulls on the Moon, keeping it in orbit around our planet.



 



Picture Credit : Google


How plants spread their seeds?



Seeds contain everything needed to form a new plant. To do that, they need to be scattered away from the parent plant to a new place on the soil where they can grow. Different types of plant have different ways of spreading their seeds. Some need animals to move them, while others use wind or even fire to scatter them.



Blow in the wind



Some plants have very light seeds and so can use the wind to spread them. This dandelion has seeds with tiny parachutes that allow them to be carried away when the wind blows.



Tasty treats



Many plants have seeds that are hidden inside tasty fruits, such as berries. When an animal eats the fruit, the seeds pass through its body unharmed and are released in its droppings.



Sticky seeds



Animals can carry seeds away from plants without even realizing it. Sticky seeds will fix on different parts of their body, while some seeds, called burs, have little hooks that attach to the animal’s fur.



Exploding pods



The Himalayan balsam plant keeps its seeds in pods. These pods explode when they are ripe, shooting the seeds out of them. The explosion can scatter the seeds up to 7 m (22 ft) away, often startling unsuspecting passers-by.



Earth, wind, and fire



Some plants have more dramatic or unusual ways of spreading their seeds. Fire may kill the parent plants, but it leaves behind fertile ash for their seeds to grow in.



Heat treatment



Jack pine cones are glued shut with resin. When a fire sweeps through the trees, the resin melts and the seeds are released.



Desert rover



Tumbleweed is the dried-up top part of some plants. It rolls around the desert whenever the wind blows, scattering its seed as it goes.



 



Picture Credit : Google


What are Plants?



Plants make their own food using sunlight. Most plants are held in the ground by their roots, and have green leaves. There are thousands of types of plants, ranging from huge oak trees to small ones like this fuchsia.



Roots



Plants usually grow in the earth or soil. The roots dig deep into the ground, keeping the plant in place. They also soak up mineral salts and water from the soil.



Stem



The stem supports the leaves and flowers holding them up towards the light. The stem also carries water and nutrients in the form of mineral salts from the roots to the rest of the plant.



Leaves



Plants use their green leaves to capture energy from the Sun’s rays. The leaves use this energy, together with carbon dioxide from the air, and water, to make food for the whole plant.



Flowers



Most plants have flowers for reproduction. They have male pollen and female eggs, which join together to make seeds.



Berries



Fruits, such as berries, are the parts of flowering plant that contain seeds. Once in the ground, the seeds will grow into new plants.



Why we need plants?



Nearly every animal relies on plants in some way or other. Some animals, called herbivores, eat only plants. Human grow lots of types of plants just for their flowers. Some types of tree are grown for their wood.



 



Picture Credit : Google


What are Living things?



All living things have certain characteristics in common. To count as being alive, a living thing has to be able to carry out seven different processes, which are listed below.



Movement



All living things can move on their own. Even plants have leaves that turn to face the Sun.



Reproduction



Living things can produce new versions of themselves.



Sensitivity



Living things can detect and respond to changes in the world around them. For example, the ability to react to changes in light, or to hear sounds.



Growth



Living things get bigger as they get older until they reach their full size.



Respiration



All living things turn food into energy, using oxygen from the air.



Excretion



All living things must get rid of any waste that they produce.



Nutrition



All living things need food. Unlike animals, plants make their own food.



Animal



Animals can move from place to place. They cannot make their own food, so they rely on eating other living things to survive.



Plant



Plants are fixed in the ground, but their roots, leaves, and flowers can move. They make their own food by using the Sun’s rays.



Fungus



Funguses may not look alive, but they are. Most funguses feed on the remains of dead plants or animals. Mushrooms, toadstools, and moulds are all funguses.



Tree trunk



When a tree dies it usually falls to the ground. Funguses can grow on the dead tree trunk and soak up its nutrients.



 



Picture Credit : Google


What are Magnets?



Magnets are objects that produce an invisible force called magnetism. When two magnets are close to each other they produce pushing or pulling forces on one another. Magnets can also pull on, or attract, other objects that are made of magnetic materials, such as iron. Magnets are often U-shaped, like a horseshoe.



Magnetic poles



Magnets have two ends, or poles, called a north pole and a south pole. Unlike poles pull on each other, or attract, so a north pole pulls a south pole. Like poles push on each other, or repel, so a north pole pushes another north pole away.



Magnetic materials



Iron is a magnetic material, so any metal with iron in it, such as steel, will be attracted to a magnet. Nickel and cobalt are also magnetic metals.



Non-magnetic materials



Magnets have no effect on non-magnetic materials. Non-magnetic materials include all non-metals, such as glass, plastic, or wood. Most metals are also non-magnetic, including gold, aluminium, and copper.



 



Picture Credit : Google


What are Electrical circuits?



An electrical circuit is a loop around which electrical energy can move. Electricity travels from a power source, such as a battery, through wires, and back to the power source. In a simple circuit, other useful items that make use of the electricity, such as a bulb or a buzzer, are added. Electricity can only flow when there is a complete circuit.



Battery



A battery stores electrical energy and releases it when connected to a circuit. The battery will eventually run down and will have to be replaced.



Switch



A switch allows the bulb to be turned on or off without removing the battery. When the switch is closed, the circuit is complete and the bulb lights up.



Wires



Electricity flows around the circuit through a series of wires. Wires are usually made of copper, as copper is a good conductor of electricity.



Bulb



As electricity flows through the bulb, the electricity energy is converted to light energy, and the bulb glows brightly.



Conductors and Insulators



Conductors allow electricity to flow easily through them. Metals, such as copper, are good conductors of electricity. Electrical wires are made of metal so electricity can flow easily through them. Insulators do not let electricity pass through them. Plastic, rubber, and wood are good electrical insulators. Wires are coated in plastic to prevent you from getting an electric shock if you touch them.



Switching on!



Many electrical items do not need batteries as they can be plugged into the mains, using a long wire. Once they have been plugged in, these items are usually turned on by passing a switch, which completes the electrical circuit.



 



Picture Credit : Google


What is Electricity?



Electricity is a type of energy that can either flow from one area to another or build up in one place. Humans have invented ways of capturing other forms of energy and using them to make electricity. Many things in our homes, such as lights, are powered by electricity.



Into our homes



After electricity has been made by a power station, it travels to towns and homes along a series of underground or overground cables. The electrical cables send electricity into the plug sockets found in most buildings. This is called mains electricity.



Static electricity



Sometimes electricity energy builds up in one place. This is called static electricity. The build-up can happen when things are rubbed together, like a balloon and a jumper, which can cause them to stick together. When a build-up of electrical energy is released, a spark of electricity can sometimes be seen or felt.



Lightning



A lightning bolt is a giant spark of electricity. When rain clouds rub against the air around them, static electricity builds up. If the build-up gets big enough, the electrical energy leaps to Earth as a bolt of lightning.



 



Picture Credit : Google