General Science Mixed Quiz: Set 156

Planck's constant has the same dimensions as angular momentum, [M L² T⁻¹].

Entomology is the branch of zoology that deals with insects, the largest class of animals, and it covers their structure, classification, life cycles and their role as pests and pollinators.

The vehicle goes 100 m east and 200√2 m south, and the straight-line distance between start and finish is √(100² + (200√2)²) = 300 m. Each leg starts from rest, so the distance covered is s = ½at².

Pellagra is caused by a lack of vitamin B3, niacin, also called nicotinic acid, and is remembered by the three Ds: dermatitis, a rough dark rash on skin exposed to sunlight, diarrhoea from the gut, and dementia from the nervous system; untreated, a fourth D, death, follows.

In free fall all the potential energy turns into kinetic energy, so 625 J = ½ × 0.32 kg × v², which gives v = 62.5 m/s. First change the mass into kilograms: 320 g = 0.32 kg.

A barometer measures the pressure of the atmosphere, and the mercury barometer invented by Evangelista Torricelli in 1643 does so by balancing the weight of the air against a column of mercury about 76 centimetres high at sea level.

A Carnot engine is an ideal reversible engine, not an irreversible one, and its efficiency is 1 − T2/T1 with temperatures in kelvin.

Wetting is decided by a contest between two forces: cohesion, the attraction among the molecules of the liquid itself, and adhesion, the attraction between the liquid and the solid surface.

The frequency of a wave is set by its source, so it does not change when light passes from air into glass; only the speed and wavelength change.

Bronze is an alloy of copper and tin, usually about 88 per cent copper to 12 per cent tin. Tin makes copper harder and gives it a far better resistance to rust and sea water, which is why bronze is used for statues, temple bells, coins, medals and ship fittings.

Beats are heard when two sound waves of slightly different frequencies overlap, so their combined loudness rises and falls regularly.

Polyvinyl chloride has linear chains held to one another only by weak forces, so it softens when heated and hardens when cooled and can be melted and moulded again and again; that reversibility is what makes a plastic thermoplastic, and it is also what allows such plastics to be recycled…

Magnetic field lines are always closed curves, so the statement that they are open curves is the incorrect one. Outside a magnet, field lines run from the north pole to the south pole; inside the magnet they continue from the south pole back to the north pole, closing the loop.

Mosses and liverworts grow on damp soil, rocks and tree trunks, that is on land, but they have no vascular tissue and their male gametes must swim through a film of water to reach the female gamete, so reproduction fails without water; living on land and breeding in water is…

The atomic number, the number of protons in the nucleus, decides which element an atom is, and no two elements share it.

It is the innermost of the three ear ossicles of the middle ear and is shaped like a stirrup; it passes vibrations from the incus to the oval window of the inner ear and is the smallest bone of the body.

. When quicklime reacts with water a large amount of heat is released, so the reaction is exothermic.

A soda-acid extinguisher uses sodium hydrogen carbonate (baking soda) solution and sulphuric acid, which react to release carbon dioxide. In this extinguisher the sulphuric acid is kept in a separate container inside a cylinder filled with sodium hydrogen carbonate solution.

This statement is false, because diamond is an electrical insulator: all four valence electrons of each carbon atom are locked in covalent bonds, leaving no free electrons to carry current.

Triclosan is an antibacterial and antifungal agent added mainly to personal-care products. It has been used in antibacterial soaps, hand washes, toothpastes, deodorants, shaving creams, mouthwashes and cosmetics, and sometimes in kitchen items and textiles to stop the growth of germs.