General Science GK Questions with Answers – Page 7

Probiotics are live, helpful microbes taken in food or supplements to improve the balance of bacteria in the gut. The word means "for life", the opposite of antibiotic, "against life".

A positive power means a converging (convex) lens, and f = 1/P = 1/2 = 0.5 m. The power of a lens is the reciprocal of its focal length in metres: P = 1/f. Its SI unit is the dioptre (D), and 1 D is the power of a lens…

Using kinetic energy = ½mv² with the mass in kilograms gives a speed of exactly 10 m/s. First convert the mass to SI units: 2000 g = 2 kg.

SONAR sends out ultrasonic pulses and times their echo from underwater objects. SONAR stands for Sound Navigation and Ranging.

This follows from Newton's third law and his law of gravitation. Newton's law of gravitation gives the force between two bodies as F = Gm₁m₂/r².

Resistivity is a property of the material itself, so changing the length of a copper wire does not change it.

. A Fischer projection draws a molecule as a cross: the horizontal bonds point towards the viewer and the vertical bonds point away.

Ammonium chloride sublimes: on heating, it changes directly from a solid into vapour without melting, and the vapour turns back into solid on a cool surface.

. A simple astronomical (refracting) telescope uses two convex, that is convergent, lenses.

Functional group isomers have the same molecular formula but different functional groups. Alkyl halides such as C2H5Cl can only contain the halogen group, so no other functional group can be built from the same formula; they show chain and position isomerism instead.

Helicobacter pylori is a spiral-shaped bacterium that lives in the lining of the stomach. It survives the strong acid by producing the enzyme urease, which makes ammonia around it, and it inflames and weakens the protective mucus layer, so acid can damage the wall and cause a peptic ulcer.

Cardiac muscle, found only in the wall of the heart, is made of cylindrical cells that branch and join with one another, and each cell usually has one central nucleus.

. For a stone whirled in a circle, the string pulls it towards the centre, while the stone moves along the circle, tangent to it at every instant.

What looks like a single flower in a sunflower or marigold is really a head made of many tiny flowers, called florets, packed together.

Vitamin K is needed by the liver to make prothrombin and other clotting factors, without which blood does not clot properly.

At sunrise and sunset sunlight passes through a much thicker layer of air, which scatters away most of the blue light and leaves mainly red and orange to reach our eyes.

Using v² = u² − 2gh with final velocity zero at the top, u = √(2gh) = √(2 × 10 × 20) = √400 = 20 m/s. A ball thrown straight up slows down under gravity until its velocity becomes zero at the highest point.

By Archimedes' principle, the upward force, called buoyancy or upthrust, equals the weight of the fluid displaced by the body.

The juice in the stem of sugarcane is rich in sucrose, the ordinary table sugar we get from it. Sucrose is a disaccharide (C₁₂H₂₂O₁₁) made of one glucose and one fructose unit joined together.

Biogas is mostly methane, usually about 50 to 75 per cent, and methane is the part that burns. Biogas is made when bacteria break down cattle dung, crop waste, kitchen waste or sewage in the absence of oxygen, a process called anaerobic digestion, inside a closed digester.