General Science GK Questions with Answers – Page 99

By the work-energy theorem the work done by a force equals the change in kinetic energy, so the work here is half of 4 kilograms times 5 metres per second squared, that is 0.5 into 4 into 25, which gives 50 joules.

Work done is force multiplied by the displacement along the force, so F equals the work divided by the distance, that is 480 joules divided by 15 metres, which gives 32 newtons.

A convex mirror bulges towards the viewer and always gives a virtual, erect and diminished image, so whatever your distance from it, your reflection looks smaller than you.

Pisciculture is the rearing of fish in ponds, tanks and other managed waters, the Latin word piscis meaning fish.

Protein synthesis begins with transcription, in which the message of a gene is copied from DNA into messenger RNA, so the first event is the making of an mRNA copy.

An ordinary filament bulb is filled with a mixture of argon and nitrogen because both are chemically unreactive and will not burn the white-hot tungsten filament.

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.

Reduction means the loss of oxygen or the gain of hydrogen, so each statement states one half of the same definition.

Hooke's law holds only as far as the limit of proportionality, and that limit is either equal to or lower than the elastic limit, so statements 1 and 4 are the correct pair.

Silver bromide is the standard example of an ionic crystal that carries both kinds of point defect at the same time.

In a thermoplastic the polymer exists as long linear or lightly branched chains, and one chain is held to the next only by weak secondary forces such as van der Waals attraction.

Flatworms, the phylum Platyhelminthes, have an incomplete digestive system with just one opening, so the same mouth takes the food in and throws the waste out.

The focal length of a mirror does not depend on the medium around it, so a convex mirror of focal length f in air keeps the focal length f inside the liquid.

Copper turns green because its surface slowly reacts with the air and gets covered by a layer of corrosion products, and that layer is green.

None of the three substances listed slows a reaction down; the substance that does that is called a negative catalyst or an inhibitor.

Dry ice is solid carbon dioxide. At ordinary pressure it does not melt into a liquid at all: it changes straight from solid to gas, a process called sublimation, at about minus 78.5 degrees Celsius.

Litmus is a purple dye taken from lichens, and in the classification used in school science lichens are placed in Thallophyta, the group of simple plants whose body is an undifferentiated thallus with no true root, stem or leaf.

Phosphorus, sulphur, chlorine and argon all sit in the third period of the periodic table, so their electrons fill the same three shells.

Group 15, the nitrogen family, holds nitrogen, phosphorus, arsenic, antimony and bismuth. Only nitrogen and phosphorus are non-metals; arsenic and antimony are metalloids and bismuth is a metal, so the group has exactly two non-metallic elements.

A pH of 11.6 means the soil is strongly alkaline, so it has to be treated with something acidic, and aluminium sulphate is the only acidic compound in the list.