General Science Mixed Quiz: Set 158

When only conservative forces do work on a system, the sum of its kinetic and potential energy stays the same; this is the principle of conservation of mechanical energy.

Speleology is the exploration and scientific study of caves, their formation, the limestone features such as stalactites and stalagmites that develop in them, and the animal life adapted to permanent darkness.

Ultrasound is sound with a frequency above 20,000 hertz, the upper limit of human hearing, so its defining feature is a higher frequency than audible sound.

Crown gall is caused by the bacterium Agrobacterium tumefaciens, which enters through a wound near the base, or crown, of the stem and makes the plant grow rough tumour-like swellings there.

Fleming's right-hand rule is used for electromagnetic induction, as in a generator, and its middle finger gives the direction of the current induced in the conductor.

In 1905 Einstein explained the photoelectric effect by treating light as made of packets of energy, later called photons, and he received the 1921 Nobel Prize in Physics for this work.

NCERT's Class 10 chemistry chapter on acids, bases and salts states that our body works within the narrow pH range of 7.0 to 7.8, which is slightly basic.

The total mass of the reactants equals the total mass of the products, which is exactly what this law states.

The statement is false because CaSO4·2H2O is gypsum; Plaster of Paris is calcium sulphate hemihydrate, CaSO4·½H2O. When gypsum is heated to about 373 K, it loses three-quarters of its water and becomes Plaster of Paris, a white powder.

When a wire is stretched its volume stays the same, so the length must grow in the same ratio as the cross-sectional area shrinks.

In 1665 Hooke looked at a thin slice of cork under his self-made microscope, saw tiny box-like compartments and named them cells, from the Latin word cella, meaning a small room.

A perfectly horizontal rope has no upward component of tension, so no finite tension can hold up the 200 N weight with the rope fully straight.

The bronchi only carry air between the windpipe and the lungs; their walls are too thick for oxygen and carbon dioxide to pass into the blood, so no gas exchange happens there.

The correct answer is B, Jharkhand, the leading lac producing state of India, which also explains why the country's lac research institute stands at Namkum near Ranchi.

. Thyroxine sets the body's basal metabolic rate, that is, how fast cells use oxygen and food to release energy.

The restoring force on the bob is mg sin θ. For small angles sin θ is almost equal to θ, so the force becomes proportional to the displacement and points back towards the mean position.

Scurvy is caused by a lack of vitamin C, or ascorbic acid, which the body needs to make collagen, the protein that holds skin, gums and blood vessels together.

Salmonella typhi is a rod-shaped bacterium that causes typhoid fever in human beings. Typhoid spreads through food and water contaminated with the faeces of an infected person.

After fertilisation each structure of the flower turns into the next stage in exactly this way. When a male gamete from the pollen tube fuses with the egg cell inside the ovule, the fertilised egg becomes the zygote.

The Geiger-Müller counter detects and counts the ionising radiation given out by radioactive substances, so it is the standard instrument for measuring radioactivity.