Why does a top spin? The spinning of the top can be explained by the term ‘gyroscopic inertia’ A spinning body will continue to spin because of inertia Suppose there was an imaginary line through the centre of the top, it would point in the...
What is a hormone? Hormones are secretions of the endocrine or ductless glands. Organs like the liver and kidney also produce some hormones. The function of hormones is to regulate the internal activities of the body like growth, nutrition, use of food materials and reproduction.
Why do pipes crack when the water in them turns to ice? Most substances shrink when they change from liquid to solid state. But water is one exception. When water becomes solid or ice, it expands by around one ninth of its volume. So 9...
How is wind speed measured? The instrument used to measure the wind speed is called anemometer. It was discovered in 1667 by an Englishman called Robert Hooke. An anemometer usually consists of some aluminium cups on a spindle. The cups turn with the wind and...
How do zips work? Zips have two rows of teeth. These are joined together by a sliding key. The key locks the teeth together or pulls them apart. The zip fastener was first invented by an American, Whitcomb Judson, in the 1890s. But the interlocking...
Do winds have different names? Not all winds have names but some do have special names. Such names have been acquired for certain reasons. The doldrums are found near the equator. Here, there is a great belt of rising air and low pressure. Such winds...
When were bacteria discovered? The first high-powered microscope was made by Antoine van Leeuwenhoek, a Dutchman. It could magnify things up to 200 times. In 1683, he published some sketches of bacteria. These are tiny living organisms which can cause disease.
What is an artesian well? In an artesian well, the water leaps into the air like a geyser from under the earth. Sometimes a layer of porous rock or sand is buried between two layers of solid rock which water cannot permeate. At some point...
When did dinosaurs inhabit earth? Dinosaurs first appeared about 230 million years ago. This was the Triassic period, when the continents formed a single mass called Pangae Around 145 million years ago, was the Jurassic period when Africa and Europe began to drift away from...
Why is the planet Mercury so hot? Mercury spins very slowly on its axis when it travels around the sun. This means that a point on its surface is exposed to the sun for almost six months (as on Earth) at a time. This makes...
