100 Important Scientific Reasons: Rain Water and the Manhole Covers are Generally Round

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22) Rain water is more fertile than water from tube well.

Ans: Rain water is more fertile because it contains many salts and nitrogen dissolved from the atmosphere.

23) The manhole covers are generally round.


  • 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.

24) Clothes of a moving dancer bulge.

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

25) People are advised not to stand near fast moving train.

Ans: 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.

26) The image of a tree is inverted on the bank of a lake.

Ans: The water of lake acts as a mirror. According to the laws of light, mirror forms inverted images.

27) Polar star is always seen in the north.

Ans: It is because the Polar Star (North Star) is closest to the location of the celestial North Pole.

28) We never see birds urinating.

Ans: The birds do not have a urinary system like other living beings which possess urinary excretory organs. In the birds the urine is excreted from body without special organs.

29) Pasteurized milk has more nourishment than the ordinary boiled milk.


  • Pasteurized milk is obtained by heating milk at a temperature of 60 degree Celsius for 30 minutes. In this way the TB bacteria are killed without damaging the milk protein.

  • Thus, pasteurized milk has more nourishment than ordinary boiled milk.

30) Bees die when they sting human being.


  • Their stingers are actually ovipositors, tubular structures extending from the abdomen that sometimes contain eggs. When the barbed stinger is left inside the victim, the honeybee mortally tears her abdomen in the process.

  • They leave their stingers in the wound with a tiny venom sac attached. Fortunately, only about one out of a hundred people are allergic to bee sting, but allergic reactions can be very serious.

31) Cloudy nights are usually warmer than the clear ones.

Ans: The clouds serve as a barrier and prevent the loss of heat. Thus, the warm temperature is maintained.

32) Why do some people snore?

Ans: Some people snore during their sleep because the breathing action produces sound. This is so because the pharynx or the windpipe offers resistance to the air taken in or expelled.

33) Why do we sometimes sleep walk?


  • Sleep walk is a sort of disorder of sleep in which a person starts walking during his sleep.

  • The sleeper walks and performs complex activities automatically without regaining consciousness.

34) Climbers bend forward while climbing mountain.


  • While climbing a mountain, a climber bends his body forward in order to keep the centre of gravity of his body within two thirds portion.

  • According to this principle the Pisa Tower is not falling.

35) Why climbers get their food by climbing on other trees?

Ans: The climbers are mostly parasites and they cannot manufacture their food. Therefore, they climb on other trees and get food from them.

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