What is a Mouse?

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An input device that is used to point and select an option on the VDU is called a mouse. The basic features of a mouse are a flat-bottomed casing designed for gripping by one hand; one or more buttons on the top; a multidirectional detection device (usually a ball) on the bottom; and a cable connecting the mouse to the computer. By moving the mouse on a surface (such as a desk top), the user typically controls an on-screen cursor. The user presses one of the mouse's buttons, producing a 'mouse click‘ to select items or choose commands.

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Which Mammals Fly in the Dark?

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B ats are the only mammals which can truly fly in the dark. They are nocturnal and so are active and fly at night. The wing of a bat is different from the wing of a bird. It is a skin-like membrane, the patagium , stretched between enormously long arm and hand finger bones. Most bats are insectivorous while some are fruits-eating. The vampire bats feed on the blood of large mammals and some others feed on mice, voles, frogs and fish. Bats are able to find their prey and avoid obstacles in the dark by using a sound radar system called echolocation. They emit very high-pitched pulses of sound called ultrasound which cannot be heard by us. The sound waves bounce back to the bat after hitting an object . The bat hears the patterns of these echoes and analyses it to give a 'sound picture‘ of the object and the surroundings.
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What are Deciduous Trees?

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What is the Sun's Corona?

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When the moon passes completely in front of the Sun during an eclipse, a glowing halo shines out. This is known as Corona or Sun's atmosphere. But it, in no way, resembles our atmosphere. It has a temperature of a million degrees centigrade and is a million times thinner than air. Normally , it hides from the view due to the Sun's brilliance except during an eclipse The Corona contains hydrogen, nitrogen oxygen and other common elements. They are very hot and scattered far apart. Unlike our atmosphere, which is held to the Earth by gravity, corona is pouring off into space at a speed of about 400Km/s. These clouds of atoms pass the planets and the Sun towards the stars. This movement of atomic particles is called solar wind.
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When were the First Mechanical Clocks Made?

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The first mechanical clocks are believed to have been made in China in 1088 AD. Later in 1200s, they were first made in Europe. Such clocks made in Europe were driven by a weight on the end of a cord wound round a drum. As the drum rotated, it turned the hands of the clock. The earliest known clock was made in Spain in 1276 AD and the oldest mechanical clock that still works is in Salisbury cathedral in Britain. It was made in 1368. These clocks had devices called escapements to keep the hands turning at the correct rate, so that the clocks depicted the correct time.
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