SCIENTIFIC REASONING QUESTIONS FOR ALL COMPETITIVE EXAMS

81) Why do water pipes burst in severe cold winters?
Ans: Water freezes in pipes during winters, when the temperature goes below 0 degree Celsius (i.e.,
freezing point of water). It expands and in the process exerts pressure on the water pipes, thereby
sometimes bursting them.
82) Most aircrafts and ships have their front shape pointed. Why?
Ans: The shape of many objects, viz. aeroplanes, rockets, ships, etc. moving through air or water, are
designed in such a way that friction can be reduced between the objects and air/water. Such type of
body is known as streamlined and the process is known as streamlining.
83) An athlete runs some distance before taking jump, why?
Ans: An athlete runs a certain distance before actually jumping in order to increase his speed, and
thereby, his inertia of motion. This increased inertia of motion enables him to jump a longer distance.
84) It is difficult to drown in the Dead Sea. Why?
Ans: The water of Dead Sea has a salt content of 27%. Therefore, its density is much greater than that
of ordinary sea water and it also offers a greater upthrust. Hence, the body weighs less than an equal
volume of Dead Sea water and is thus, able to float.
85) Why aquatic animals have soft skeleton unlike those of the terrestrial animals?
Ans: The density of animals and fish living in water is almost the same as the density of water.
Therefore, their weight is almost completely balanced by buoyancy. That is why they do not need
massive skeleton like those of terrestrial animals.
86) Why does a swimming pool appear less deep than it really is?
Ans: When rays of light start from the bottom of a pool and travel from water to air, they are
refracted away from the normal because they travel from a denser medium to a rarer medium. As a
result, a virtual image of bottom is formed above the bottom. Hence, a swimming pool appears less
deep than it really is.
87) Why is electrical wiring in parallel better?
Ans: electrical wiring in parallel is better because all the lines will have the same potential difference
and if one line gets fused the other lines remain unaffected.
88) It is easier to swim in sea water than in river water. Explain.
Ans: The density of sea water is more than that of the river water. Therefore, the weight of sea water
displaced by the swimmer is more. Thus, buoyant force of upthrust on the swimmer increases,
making it easier to swim in sea water.
89) A cold compress is applied on the forehead of a person suffering from high fever. Why?
Ans: Evaporation causes cooling. As the water evaporates, it absorbs heat from the forehead and
helps in reducing the temperature.
90) A man with a load his head jumps from a high building. What will be the load experienced by
him.
Ans: Zero, because the acceleration of his fall is equal to the acceleration due to gravity of the earth.