SCIENCE-Q&A

Why Do Cows Have Four Stomachs?

- A cow is a big animal that eats grass and other tough plants. It eats a large amount of food everyday. It needs four stomachs to break down and digest its food properly. Each of the four stomachs has a special job to do.

When a cow feeds on grass, it gives the grass a quick chew with its back teeth and swallows it. The partly chewed grass goes into the cow’s first stomach called the rumen. In side the rumen, the grass is broken down into ‘balls of cud’. When the rumen is full, the cow stops eating and rests. While it rests, the cow brings back each ball of cud into its mouth and chews it into a soft pulp. Then it swallows the pulp again.

The mushy pulp goes through the second and third stomachs where the harder bits of the pulp are filtered out. These tough bits go back to the rumen and the process starts all over again. The rest of the pulp goes on to the last stomach where it is completely digested.

The cow puts its food through many rounds of digestion and absorbs the nutrients at the end. This means that a cow is only healthy if all of its four stomachs are in good working order.

      

Why do Volcanoes Erupt?

-A Volcano can be a mountain or hill that has an opening at the top. The opening is called the vent and it leads deep down into the earth. When a volcano erupts, hot melted rock, gas and ash from inside the earth burst out through the vent.

Below the Earths surface crust is a layer called the mantle. The mantle is made up of melted or molten rocks called magma. The intense heat from the mantle forces the magma upward towards the Earths surface. The hot, runny magma squeezes along any crack or passage. A volcanic eruption occurs when magma shoots out through the vent of a volcano. The magma that shoots out is known as lava.

In every volcanic eruption, there is incredible heat. In some eruptions, however, the lava is much hotter that in others. If erupting lava is very hot, it flows down the side of the volcano like a liquid. It can flow for tens of kilometers before it cools into solid rock. If erupting lava is cooler, there may be explosions as lumps of lava together with volcanic ash are thrown high into the air. Volcanic ash may be blown far away from the erupting volcano by winds before it settles. It breaks down quickly and becomes fertile soil.

-A volcano may be active, dormant or extinct. An active volcano often erupts. A dormant volcano has not erupted for a long time. A extinct Volcano no longer erupts.

Why is Lightning seen before Thunder is Heard?

-When there is a thunderstorm, flashes of light are seen in the sky, and loud rumbles or bangs can be heard. The flashes of light are called lightning and the loud noises are called thunder.

Lightning is a huge electrical spark in the sky. It is caused by a build-up of electricity inside a thundercloud. Drops of water and crystals of ice whizz about and collide with each other inside the cloud. When they collide, they create a electrical force.

Eventually, the electrical force becomes very strong. The force becomes so strong that it jumps through the air to other clouds or down to the ground. As the electrical force jumps, sparks of lightning can be seen. The lightning heats up the air that it passes through. The air expands very fast and makes a sound like an explosion. The sound is called thunder.

Light travels very fast, at about 300,000 kilometres per second. Sound, however travels more slowly, at only 0.33 kilometre per second. This difference in speed is the reason why lightning is seen before thunder is heard.

Why do Rainbows appear when it is both Sunny and Raining at the same time?

-A rainbow is an arch of seven colours of light that is seen in the sky. Rainbows can usually be seen in the morning or afternoon, when it is about to rain, during the rain or after rain.

Sunshine consists of straight rays of light that reach the Earth from the Sun. Sunlight is called ’white light’. When the straight rays of white light bend, they separate into seven bands. Each band is a different colour and they are always in the same order: Red, Orange, Yellow, Green, Blue, Indigo and Violet.

When a ray of sunlight hits and enters a raindrop, the raindrop’s round surface bends the ray. The white light separates into seven colours and forms a tiny rainbow inside the raindrop.

Then, the mini rainbow is reflected from the back of the raindrop. It is bent again as it passes out through the curved surface of the raindrop.

The arched shape of a rainbow occurs because the rays of light are bent twice, once on the way in and once on the way out of each raindrop. This is why there must be both sunshine and raindrops at the same time to make a seven-coloured rainbow.