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Science & Mathematics Questions & Answers

Science & Mathematics Questions & Answers

Why is sea water very high in salt content?

The average salinity of sea water is about 3.5%. One cubic mile of sea water contains 166 million tonne of salt. The salts of the sea come from the breaking up of rocks and gradual wearing away of mountains releasing salts that are washed down by rainwater. It is estimated that more than 400 million tonne of dissolved salts are …

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Why is radioactivity dangerous?

Radioactivity is dangerous because it can expose people to a harmful dose of radiation even without being aware of it. A number of small doses received over a very long time could lead to leukaemia or cancer in later life. Radiation can lead to the retention of a potentially harmful amount of radium in one’s bones. Radioactivity resulting from nuclear …

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Why is quartz used in watches?

Quartz is used in watches as it acts as a piezoelectric oscillator. As a potential difference is applied across quartz, stress is generated across the perpendicular faces of the quartz crystal. It is known as reverse piezoelectric effect. The word piezo in Greek means pressure and, therefore, piezoelectricity means pressure electricity. It takes place in some crystals like quartz which …

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Why is Prince Henry of Portugal called ‘The Navigator’?

Prince Henry was the fifth son of King John I of Portugal and of Queen Philippa, grand-daughter of Edward III of England. In his youth he had proved himself to be a brave warrior, but his one desire in life was to extend the sea-routes of the world and to make his country rich by trade. He set up an …

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Why is pig iron called so?

Pig iron is the intermediate product of smelting steel ore with coke and resin. Pig iron has a high carbon content, typically 3.5-4.5%, which makes it brittle and not useful directly as a material except for limited applications. The traditional shape of moulds used for these ingots was a branching structure formed in sand, with many individual ingots at right …

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Why is mercury called the forgotten planet?

Mercury can claim the title for the “weirdest” planet in the solar system, apart from being the smallest and the innermost. It has the wildest temperature extremes – from 800’c to to 300’c and drifts from being the nearest to being the farthest from the sun. Reaching mercury poses significant challenges as the planet orbits close to the sun. Hence, …

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Why is liquid ammonia used in ice plants?

Liquid ammonia acts as a refrigerant in ice plants. Evaporation of a liquid needs heat energy. When liquid ammonia vapourizes, it absorbs large quantities of heat without changing its temperature. For these reasons, ammonia is widely used as a refrigerant. About 17 g of liquid ammonia absorbs 5,700 calories of heat from the surrounding water. This cools the water and …

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Why is it harder to walk uphill than downhill?

It is harder to walk uphill than downhill because you must lift the weight of your body and to do this requires greater energy than that needed for walking on the level. To create this greater energy your muscles require to give extra lift, your heart has more work to do to feed the blood cells and remove their waste …

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Why is it cooler at higher altitudes?

High altitudes normally begin at 1500 metres above sea level. At such altitudes, the atmospheric pressure is considerably lower than at sea level. To give some examples: the pressure at sea level is 14.7 pounds per square inch and it decreases through 4.3 psi at 30,000 ft to 1.6 psi at 50,000 ft. Because of this, the air expands as …

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