scientist, discoveries & inventions MCQ section 3 Practice Questions Answers Test with Solutions & More Shortcuts

Answer: (d)

Lactometer is a device used to measure the specific gravity, and therefore the richness, of milk.

It is based on the law of floatation which states that when a solid is immersed in a liquid, it is subject to upward thrust equal to the weight of the liquid displaced by the body and acting in an upward direction. It is useful for testing the purity of milk.

Answer: (c)

Nicolaus Copernicus discovered the Solar System. He was the first astronomer who formulated a comprehensive heliocentric cosmology in his book "De Revolutionibus Orbium Coelestium" (On the Revolutions of the Celestial Spheres), which displaced the Earth from the center of the universe.

Answer: (a)

A planimeter, also known as a platometer, is a measuring instrument used to determine the area of an arbitrary two-dimensional shape. They were once common, but have now largely been replaced by digital tools. The Swiss mathematician Jakob AmslerLaffon built the first modern planimeter in 1854.

Answer: (b)

Selman Waksman was awarded the Nobel Prize in 1952 “for his discovery of streptomycin, the first antibiotic effective against tuberculosis.” He was called “one of the greatest benefactors to mankind,” as the result of the discovery of streptomycin. Waksman was a Russian-born, Jewish-American inventor, biochemist and microbiologist.

Answer: (b)

The Wright brothers, Orville and Wilbur, were two American brothers, inventors, and aviation pioneers who were credited with inventing and building the world's first successful aeroplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903.

In the two years afterwards, the brothers developed their flying machine into the first practical fixed-wing aircraft.