General Science Previous Year Questions (PYQ) with Answers – Page 76

Surface gravity is g = GM/R², so doubling the mass doubles g while doubling the radius divides it by four, leaving g₁ × 2/4 = g₁/2.

In graphite each carbon atom is sp² hybridised, not sp³, so statement A is the one that is not true.

All three follow from Einstein's General Theory of Relativity, published in 1915. General relativity explains gravity not as a force but as the curving of space-time by mass and energy; in John Wheeler's words, matter tells space-time how to curve, and space-time tells matter how to move.

Lysosomes bud off from the Golgi apparatus as small membrane-bound sacs packed with digestive enzymes. The hydrolytic enzymes of a lysosome are first made on ribosomes attached to the rough endoplasmic reticulum.

When natural gas or heavy oil burns with too little air, the carbon cannot all turn into carbon dioxide and separates as a very fine black soot, which is collected as carbon black.

Plaster of Paris is calcium sulphate hemihydrate, CaSO₄·½H₂O, so one molecule of water is shared by two formula units of calcium sulphate, written (CaSO₄)₂·H₂O. It is made by heating gypsum, CaSO₄·2H₂O, to about 373 K (100 °C), when gypsum loses one and a half molecules of water per formula unit.

In the order visible light → ultraviolet → X-rays, the wavelength falls and the photon energy rises, so statements 1 and 2 are true and 3 is false.

A fluid at rest presses on the walls and has pressure at every point, but that pressure is not the same at all depths.

Zero on the Kelvin scale lies 273.15 degrees below the freezing point of water. The Kelvin and Celsius scales have degrees of the same size, so T(K) = t(°C) + 273.15.

The slightest push makes the ball fall off and it does not come back. A body is in unstable equilibrium when a small displacement lowers its centre of gravity, so the forces acting on it move it further away instead of back.

Nereis, the sandworm, moves with parapodia, paired fleshy flaps on the sides of its body segments, not with pseudopodia. Nereis is a marine annelid.

Halophytes are plants of saline soils, chiefly the mangroves of tidal creeks and deltas such as Rhizophora and Avicennia, and their morphology is shaped by that habitat: they bear pneumatophores, negatively geotropic breathing roots that rise out of the waterlogged mud, along with stilt and prop roots for support and…

The zygote is diploid (2N) and the primary endosperm nucleus is triploid (3N). Double fertilisation is a feature of flowering plants.

In a reflex arc the message runs from the sense organ to the spinal cord and straight back to a muscle or gland.

The iris is the coloured ring in front of the lens, formed by the front part of the choroid, and the muscles in it widen or narrow the pupil so that the right amount of light reaches the retina; in dim light the pupil opens wide and in bright light…

Adipocytes are the fat cells of adipose tissue, a loose connective tissue that stores fat in animals. Adipose tissue lies mainly beneath the skin and around organs such as the kidneys and heart.

Seeds are carried away from the parent plant by wind, water and animals, but fungi play no part in seed dispersal.

In photosynthesis, the oxygen released into the air comes from water molecules that are split using light energy. Photosynthesis takes place in the chloroplasts of green plants.

Oxygen-rich blood from the lungs returns through the pulmonary veins into the left auricle (left atrium) of the heart. The human heart has four chambers: two upper auricles (atria) that receive blood and two lower ventricles that pump it out.

The flying fish is a bony fish with a backbone, gills, scales and fins, so it belongs to the class of fishes; it only glides over the water on its large, wing-like pectoral fins.