General Science Mixed Quiz: Set 22

The correct answer is C, its mass. Inertia is the tendency of a body to stay at rest or keep moving in a straight line, and the measure of that tendency is mass. A heavier body is harder to start, stop or turn, so mass is called the measure of inertia. This follows from Newton's first law of motion, which is also called the law of inertia. Mass is a scalar quantity, measured in kilograms, and it stays the same everywhere. Option A is wrong because weight is the force of gravity on the body, equal to mass times the acceleration due to gravity, so it changes from the Earth to the Moon while inertia does not. Option B is wrong because mass times velocity is momentum, which describes motion already in progress. Option D is wrong because mass times acceleration is force, the cause of a change in motion. Exam tip: mass is inertia, mass times velocity is momentum, mass times acceleration is force.

The correct answer is C, a and c, that is Spirulina and Chlorella. Both are tiny algae grown in tanks and sold as protein rich food supplements, and both have been studied as food for astronauts. Spirulina is a blue green alga, really a cyanobacterium, whose dried powder is about sixty per cent protein and also carries iron and beta carotene. Chlorella is a single celled green alga that multiplies very fast in a small space and gives off oxygen as it grows, which is why space agencies have tested it in closed life support systems. Such food from microbes is called single cell protein. Option A is wrong because Spirogyra, the slippery filamentous alga of ponds, is not eaten as a supplement. Option B is wrong for the same reason, as it also carries Spirogyra. Option D is wrong because it leaves out both correct names and adds Funaria, which is a moss and not an alga at all. Exam tip: Spirulina and Chlorella give single cell protein.

The correct answer is B, Product of the masses of objects M × m. Newton's universal law of gravitation states that every two bodies attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them, written F = GMm/d². Here G is the universal gravitational constant, whose value is 6.67 × 10⁻¹¹ newton metre squared per kilogram squared. So doubling either mass doubles the force, while doubling the distance cuts the force to one fourth. A is wrong because the law multiplies the masses instead of adding them. C is wrong because a difference of masses would make the force vanish for two equal bodies, which never happens. D is wrong because no square of a mass appears in the formula; only the distance is squared. Exam tip: F = GMm/d², directly proportional to the product of masses and inversely to the square of the distance.

The correct answer is B, tuberculosis (TB). The BCG vaccine takes its name from Albert Calmette and Camille Guerin, the two French scientists who developed it from a weakened strain of Mycobacterium bovis. In India it is given as a single dose soon after birth under the Universal Immunisation Programme, and it protects infants mainly from the severe forms of the disease, such as tuberculous meningitis and miliary tuberculosis. Tuberculosis itself is caused by the bacterium Mycobacterium tuberculosis, identified by Robert Koch in 1882, and it spreads through droplets when a patient coughs. Option A is wrong because typhoid, caused by Salmonella typhi, has its own conjugate vaccine. Option C is wrong because mumps is a viral disease covered by the MMR vaccine along with measles and rubella. Option D is wrong because plague, caused by Yersinia pestis and carried by rat fleas, needs a different vaccine. Exam tip: BCG at birth for TB, and World TB Day falls on 24 March.

The correct answer is B, total internal reflection. An optical fibre is a thin thread of glass or plastic with a core of higher refractive index surrounded by a cladding of lower refractive index. Light entering one end strikes the boundary at an angle greater than the critical angle, so none of it escapes and all of it is reflected back into the core. Repeating this thousands of times, the signal travels along the fibre even when it is bent, with very little loss, which is why fibres carry telephone, internet and cable television signals and are also used in endoscopes.

Option A, dispersion, is the splitting of white light by a prism. Option C, diffraction, is the bending of waves around obstacles. Option D, polarisation, restricts the vibration of light to one plane and is used in sunglasses.

The correct answer is A, Distillation. Distillation separates a liquid from a solution or from another liquid by boiling it and condensing the vapour, so it is used when the components differ in boiling point, as in getting pure water from salt water or separating acetone from water. It is not the method for purifying a solid mixed with solid impurities. Option B is useful because sublimation purifies a solid that turns straight into vapour on heating, such as camphor, naphthalene, iodine or ammonium chloride, leaving the non-volatile impurity behind. Option C is useful because crystallization dissolves the solid in a hot solvent and lets pure crystals form on cooling, the standard way to purify alum, copper sulphate and sugar. Option D is wrong because two of the three processes do purify solids, so they cannot all be useless. Exam tip: solids are purified by sublimation, crystallization and chromatography; distillation is for liquids.

The correct answer is B, 20 Hz to 20,000 Hz. This is the band of frequencies to which a healthy human ear responds, and the upper limit falls with age. Below the lower limit the sound is called infrasonic and is produced by elephants, whales and earth movements before an earthquake; above the upper limit it is called ultrasonic and is produced and heard by bats, dolphins and porpoises.

Option A, 2 Hz to 200 Hz, lies almost entirely in the infrasonic band at its lower end and cuts off ordinary speech and music at its upper end. Option C, 200 Hz to 2,00,000 Hz, wrongly extends deep into the ultrasonic range, which no human can hear. Option D, 20 Hz to 2,000 Hz, has the right starting point but an upper limit ten times too low, which would leave out most of the higher notes of music that people hear easily.

The correct answer is B, Papaver Somniferum. Opium is the dried latex of the opium poppy, whose botanical name is Papaver somniferum; the second word means sleep bringing. The milky latex is collected by making shallow cuts in the unripe capsule, and from it come the medicines morphine and codeine, used to control pain and cough. India grows the crop only under licence from the Narcotics Commissioner at Gwalior in Madhya Pradesh, and the licensed districts lie in Madhya Pradesh, Rajasthan and Uttar Pradesh, which is why state papers ask this question. Option A is wrong because Emblica officinalis is amla, the Indian gooseberry, rich in vitamin C. Option C is wrong because Rauvolfia serpentina is sarpagandha, the source of reserpine used for high blood pressure. Option D is wrong because Cinchona species yield quinine, the old treatment for malaria. Exam tip: opium Papaver somniferum, amla Emblica officinalis, quinine from Cinchona.

The correct answer is B, potential difference. The potential difference between two points in a circuit is defined as the work done in moving a unit positive charge from one point to the other. From this definition comes the unit: one volt is one joule of work per coulomb of charge, and the quantity is measured with a voltmeter connected in parallel across the two points.

Option A, pressure distance, is not a physical quantity at all, and pressure belongs to mechanics rather than to circuits. Option C, potential distance, is likewise not a defined term; the word potential appears only to make the option look plausible. Option D, pressure difference, is a real quantity but belongs to fluids, where it drives the flow of a liquid or a gas; it is sometimes used only as an analogy for voltage while teaching, never as the name of the electrical quantity. The definition asked for is that of potential difference.

The correct answer is D, Thallophyta. Algae belong to Thallophyta, the simplest division of the plant kingdom. Their body is a thallus, which means it is not divided into root, stem and leaf, and they have no vascular tissue. Most algae live in water, make their own food by photosynthesis and reproduce by spores; Spirogyra, Ulothrix, Chara and Volvox are common examples. Option A is wrong because angiosperms are flowering plants whose seeds lie enclosed in a fruit, the most advanced group of all. Option B is wrong because pteridophytes, such as ferns, are the first plants with proper vascular tissue, though they bear no seeds. Option C is wrong because bryophytes, such as mosses and Marchantia, are called the amphibians of the plant kingdom; they stand a step above thallophytes and need water for reproduction. Exam tip: the order of the plant kingdom is Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms.

The correct answer is A, J. Chadwick. James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles and showing that the radiation produced consisted of neutral particles of nearly the same mass as the proton. The discovery explained why the mass of an atom is greater than the mass of its protons and electrons together. Option B is wrong because E. Goldstein discovered canal rays, which carried positive charge and led to the identification of the proton. Option C is wrong because Niels Bohr gave the model in which electrons revolve in fixed permitted shells without radiating energy. Option D is wrong because Ernest Rutherford discovered the nucleus through alpha-particle scattering and had only predicted that a neutral particle should exist. Note the years, which papers like to ask together: the electron in 1897, the nucleus in 1911 and the neutron in 1932, the last of the three fundamental particles to be found.

The correct answer is A, Moth. Silk comes from the cocoon spun by the caterpillar of a moth.

The common silk moth is Bombyx mori, and rearing it is called sericulture. The female lays hundreds of eggs, the larva or silkworm feeds on mulberry leaves, and when it is ready to pupate it secretes a protein thread from its salivary glands and wraps itself in a cocoon. The cocoons are treated with steam or hot water and the single long fibre is reeled off. Karnataka leads India in silk output, and India is the second largest producer after China.

Option B is wrong because goats give mohair, pashmina and cashmere, which are types of wool. Option C is wrong as sheep give wool. Option D is wrong because butterflies do not spin commercial silk cocoons; both belong to the order Lepidoptera, but only moths are reared for silk.

Exam tip: silk from the moth Bombyx mori and mulberry leaves; wool from sheep and goat.

The correct answer is C, Diamond. Carbon occurs in nature in two ways, free and combined. In the free state the element stands alone, as in diamond, graphite and coal; diamond is pure carbon whose atoms are each joined to four others in a rigid three dimensional network, which is why it is the hardest natural substance known. In the combined state carbon is locked into a compound with other elements. A is wrong as a choice because chalk is calcium carbonate, a compound. B is wrong because marble is also calcium carbonate, formed when limestone is changed by heat and pressure. D is wrong because dolomite is a double carbonate of calcium and magnesium. All three are therefore combined forms of carbon, and only diamond is the free element. Graphite, in which each atom joins three others in sheets, is also free carbon, yet it is soft and conducts electricity. Exam tip: diamond, graphite and coal are free carbon; carbonates are combined carbon.

The correct answer is D, Zygote. The fusion of a male gamete with a female gamete is called fertilisation, and the single cell it produces is the zygote. The male gamete in animals is the sperm and the female gamete is the egg or ovum. Each gamete carries half the normal number of chromosomes, so the zygote gets a full set again: in human beings 23 chromosomes come from the sperm and 23 from the egg, making 46. The zygote then divides again and again, travels down the fallopian tube and settles in the wall of the uterus. Option A is wrong because the ovum is the female gamete itself, one of the two cells that fuse, not the result. Option C is wrong because the embryo is the ball of cells formed after the zygote starts dividing. Option B is wrong because the foetus is a still later stage, when the organs have taken shape. Exam tip: remember the order gametes to zygote to embryo to foetus.

The correct answer is A, Lysosome. The lysosome is a small sac bound by a single membrane that is filled with digestive enzymes, so it breaks down food particles taken into the cell and clears out worn out parts of the cell itself. Because it can digest the whole cell when the membrane bursts, for example when the cell is injured or starving, it is often called the suicide bag of the cell, a name given by Christian de Duve, who discovered it. Its enzymes work best in an acidic setting, which the lysosome keeps inside itself. B is wrong because peroxisomes handle oxidation reactions and break down hydrogen peroxide rather than acting as the digestive system. C is wrong because glyoxysomes are found in fatty plant seeds and convert stored fat into sugar. D is wrong because a polysome is only a group of ribosomes reading one mRNA strand. Exam tip: lysosome, single membrane, suicide bag, de Duve.

The correct answer is A, Liquid. At normal atmospheric pressure water stays liquid between 0 °C and 100 °C, and 12 °C lies inside that range. Water freezes into ice at 0 °C, which is its melting point, and boils into steam at 100 °C, which is its boiling point, when the pressure is one atmosphere. Between these two fixed points the molecules have enough energy to slide over one another but not enough to fly apart, so water flows and takes the shape of its container while keeping a fixed volume. Water does evaporate slowly at 12 °C from an open surface, but that happens only at the top layer and does not change the state of the water below. Option B is wrong because ionic is not a state of matter at all; it describes a kind of bond or compound. Option C is wrong because water becomes a gas, that is steam, only above 100 °C. Option D is wrong because water turns solid only at or below 0 °C. Exam tip: remember 0 °C and 100 °C as the fixed points of water at one atmosphere.

The correct answer is C, Bile juice, Pancreatic juice. Fat is digested in the small intestine by these two secretions working together. Bile is made by the liver and stored in the gall bladder; it carries no enzyme, but its bile salts break large fat globules into tiny droplets, a process called emulsification, and they also make the acidic food from the stomach alkaline so that pancreatic enzymes can act. Pancreatic juice is poured into the duodenum and carries lipase, which splits the emulsified fat into fatty acids and glycerol, along with trypsin for protein and pancreatic amylase for starch. Option A is wrong because saliva has only salivary amylase, which acts on starch in the mouth. Option B is wrong because hydrochloric acid only makes the stomach acidic and activates pepsin, while mucus protects the stomach lining. Option D is wrong for both those reasons; neither saliva nor acid digests fat. Exam tip: bile emulsifies and lipase digests; the liver is the largest gland in the human body.

The correct answer is A, Arteries. Arteries are the blood vessels that carry blood away from the heart to the different parts of the body. Because the heart pushes blood into them under high pressure, arteries have thick, muscular and elastic walls and no valves, and they are placed deep in the body. The largest artery is the aorta, which leaves the left ventricle. One important exception is the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, so arteries are defined by direction, not by the kind of blood. B is wrong because veins bring blood back to the heart, have thinner walls and carry valves to stop backflow. C is wrong because the septum is the wall of muscle that separates the right and left sides of the heart. D is wrong because capillaries are the very thin vessels where exchange of gases and nutrients takes place. Exam tip: arteries away from the heart, veins towards it.

The correct answer is D, Testosterone. Testosterone is made by the Leydig cells of the testes and is the main male sex hormone. It controls the growth of the male reproductive organs and brings the changes of puberty in boys, such as a deeper voice, facial and body hair, broader shoulders and greater muscle and bone growth. Its release is controlled by the pituitary gland through luteinising hormone, so the testes work both as a gland and as the organ that makes sperm. A is wrong because thyroxine comes from the thyroid gland in the neck and sets the rate of metabolism; too little of it in a child causes stunted growth. B is wrong because adrenaline is released by the adrenal glands above the kidneys and prepares the body for fight or flight. C is wrong because insulin comes from the beta cells of the pancreas and lowers blood sugar. Exam tip: testes give testosterone, ovaries give oestrogen and progesterone.

The correct answer is C, Neither I nor II, because both pairs are the wrong way round. Iron is a micronutrient, needed by plants only in very small amounts, and calcium is a macronutrient, needed in large amounts. Macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium and sulphur, while the micronutrients are iron, manganese, boron, zinc, copper, molybdenum, chlorine and nickel. Iron works in chlorophyll formation and in the electron carriers of photosynthesis, so a shortage shows as yellowing between the veins of young leaves. Calcium builds calcium pectate in the middle lamella of the cell wall and holds cells together. A is wrong because the first pair calls iron a macronutrient. D is wrong because the second pair calls calcium a micronutrient. B is wrong because neither pair is correct. Exam tip: remember the nine macronutrients; anything outside that list is a micronutrient.