What do X-rays Show?

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X-rays are special photographs which are needed to detect any injury or damage inside the body. These photographs show through the soft tissues of the body, but not the bones. They show if a bone has been damaged or broken and also reveal if some organs like the lungs and heart are working properly.

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How do Aircrafts Fly?

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T o fly in the air, aircrafts need power, which is provided by the engines. They need a lift to rise from the ground and stay in the air. This lift is provided by the wings. The aircraft wings have a special shape called an aerofoil . The top surface of the wing is curved, while the bottom is flat. As the plane cuts through the air , the air that flows over the wing has to travel greater distances than the air flowing underneath the wing, so it has to travel faster over the top. This reduces the pressure above the wing and creates lift At take-off, the engine provides the power to generate lift. The forward thrust of the engines balances the resistance or drag set up by the air.
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Why is Venus so Hot?

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T he planet Venus is named after the Roman goddess of beauty and love. It is the brightest planet in the Solar System. It is visible as a star. Venus is much hotter, because it is much closer to the Sun. The atmosphere there is 90 times thicker than that of the Earth and the surface is hidden in a white cloudy cloak. This thick atmosphere acts like a blanket which holds back the heat of the Sun and turns the midday temperature to 4800C. The atmosphere on Venus consists mainly of the carbon dioxide gas which acts as a greenhouse roof , trapping the Sun's heat. The rocks on Venus are hotter than boiling water. Above the rocks, winds blow at a speed of 320 km/hour .
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When were the First Spinning Machines Invented?

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People in the olden days used to spin thread by hand . They pulled fibres out of cotton and wool and twisted them together into thread. Spinning machines were invented in Britain in the 1700s. These machines had rollers turning at different speeds to twist the fibres into yarn. James Hargreaves in 1764 produced the first successful spinning machine. It was the hand-powered jenny which produced thin yarn. Richard Arkwright's water frame of 1769, powered by water wheels, gave a sturdy thread. Samuel Crompton combined these two spinning machines in 1779 , to make the spinning mule, which could spin many kinds of yarn. These machines were the precursors of the Industrial Revolution . 
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When were the First Mechanical Clocks Made?

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