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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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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Why does Mistletoe Grow on Trees?

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M istletoe is a plant which grows on branches of higher trees. It is a partial parasite since it has green leaves containing chlorophyll and can make its own food by photosynthesis. It takes the water and minerals it needs from the sapwood of the host tree. It is found growing on trees like apple, hawthorn, willow, poplar and lime . The seeds of mistletoe are spread by birds and once the seed germinates on the host tree, it develops haustorium . The haustorium is a tough structure and ensures of a regular supply of water and nutrients from the sapwood of the host to the mistletoe. The plant then develops a clamp like structure on the tree to be placed firmly.
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Comet

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C omet A small Solar System body made of ice and dust. Comets are asteroidal in appearance at distances of many astronomical units from the Sun (when they consist of a bare , inactive nucleus), and are often spectacularly active when nearer to the Sun. The characteristic bright head (coma ) and streaming tails (both dust and ions) are created by solar heating, with emission of light from gas molecules and scattered light from the dust. The comet nucleus is a few km in size, irregularly shaped and very dark ; dust in the coma contains carbon and silica; there is evidence of polymerized organic molecules; the gases of the coma include water, carbon monoxide, carbon dioxide, ammonia, methane, and hydrocarbons. The source of comets is believed to be a spherical halo cloud about the Sun called the Oort Cloud. Observable comets are occasionally scattered into the inner Solar System by the gravitational fields of nearby stars and giant molecular clouds. Some ( eg Halley's comet) are...
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How do Trawlers Fish?

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T rawlers are vessels that fish with a large net called trawl. The trawl is a bag-like net and could be over 100 metres long. It is attached to the rear part of the vessel with long ropes, which can go down to enormous depths upto 1500 metres or more. The fish are swept in at the wide, open end and then get trapped at the narrower closed end. When the net is full of fish, powered winches bring it back to the vessel. Modern trawlers are big factories in themselves . The fish are automatically gutted, filleted and frozen there on board .
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How will the Universe End?

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No one has been able to predict the future of the Universe. It could continue as such or eventually slow down, come to a halt and fly inwards to the “Big Crunch'. The astronomers believe that the future of the Universe depends upon the amount of material it contains. The greater the amount of material, the more powerful is the gravitational force trying to pull the galaxies back together. However, the galaxies known to us do not seem massive enough to end the expansion of the universe. But they could have hidden mass which would eventually slow down and end the present expansion.
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