Scientific Reasons From Past Papers 17

➽ An athlete runs some distance before taking jump, why?
Answer: 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.

➽ It is difficult to drown in the Dead Sea. Why?
Answer: 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.

➽ Why aquatic animals have soft skeleton unlike those of the terrestrial animals?
Answer: 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.

➽ Why does a swimming pool appear less deep than it really is?
Answer: 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.

➽ Why is electrical wiring in parallel better?
Answer: 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.

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