Scientific Reasons From Past Papers 5

➽ Light colours absorb less heat therefore these are not heated as much as the black colour.
Answer: Dark colours do not exactly absorb more heat, but they do convert a higher percentage of light into heat. In the sun with a dark coloured shirt it gets hot, where a lighter coloured shirt would not get nearly as hot. This is due to the amount of light being absorbed by the colour. The lighter the colour the smaller is the range of visible light being absorbed and converted into heat. White objects reflect all visible light, where black objects absorb all visible light.

➽ Rain water is more fertile than water from tube well.
Answer: Rain water is more fertile because it contains many salts and nitrogen dissolved from the atmosphere.

➽ The manhole covers are generally round.
Answer: Manholes, which interconnect underground sewerage pipes, and serve as a point of entry for cleaning the pipes, are located at every major sewer pipe junction, and are capped with round manhole covers. The reason for the circular construction of these covers is, quite simply, that covers of any other shape would fall through the manholes by virtue of their varying diameters. Circular manhole covers do not vary in width, or in diameter, as is the case with these other shapes, thus remaining in place despite the street traffic running roughshod over them.

➽ Clothes of a moving dancer bulge.
Answer: The clothes of a moving dancer bulge outside due to the centrifugal force which tends to move away from the centre.

➽ People are advised not to stand near fast moving train.
Answer: One should not stand beside a fast moving train because of the strong pressure of air which
carries along. A man can fall in this pressure.

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