General Science GK Questions with Answers – Page 40

Mature human red blood cells lose these organelles as they develop. Red blood cells are made in the red bone marrow and push out their nucleus and other organelles before entering the blood.

The slightest push makes the ball fall off and it does not come back. A body is in unstable equilibrium when a small displacement lowers its centre of gravity, so the forces acting on it move it further away instead of back.

It is a carbon compound with a carboxyl group, so it is an organic acid. Acetic acid (ethanoic acid, CH₃COOH) contains the –COOH group typical of carboxylic acids.

Soaps are sodium or potassium salts of long-chain carboxylic (fatty) acids, not ammonium salts. A soap molecule has a long hydrocarbon tail that mixes with oil and an ionic head that faces water.

Diamond and crystalline silicon have the same crystal structure. Isomorphous means having the same crystal form.

Both quantities change with temperature, and resistance is directly proportional to resistivity, while resistivity does not depend on the wire’s size.

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.

Myopia is short-sightedness: near objects look sharp but distant ones look blurred. In a myopic eye the eyeball is too long or the eye lens is too curved, so light from a distant object comes to a focus in front of the retina instead of on it.

Each reaction is labelled with its correct type, so every pair is matched correctly. In I, iron is more reactive than copper and pushes it out of copper sulphate, a displacement reaction.

Of the four elements of xylem, only xylem parenchyma is made of living cells; tracheids, vessels and xylem fibres are dead at maturity.

Cetane is the common name of n-hexadecane, C16H34, a straight-chain alkane with sixteen carbon atoms. Cetane ignites very readily when compressed, which is exactly what a diesel engine needs, because diesel fuel is not lit by a spark but catches fire from the heat of compressed air.

A gamma ray is a photon of energy with no mass and no charge, so emitting it leaves the count of protons and neutrons unchanged.

Plaster of Paris mixed with water sets within minutes into a hard mass, which is why doctors use it to make casts that hold broken bones in place.

Nereis, the sandworm, moves with parapodia, paired fleshy flaps on the sides of its body segments, not with pseudopodia. Nereis is a marine annelid.

In grasses the intercalary meristem lies at the base of the leaf blades and internodes, between tissues that are already mature.

Evaporation from the leaves pulls a continuous column of water up the xylem, and cohesion and adhesion keep that column from breaking.

A water molecule has two hydrogen atoms of atomic mass one and one oxygen atom of atomic mass sixteen, so the masses are two and sixteen, which is a ratio of one to eight; this fixed ratio in every sample of water, whatever its source, is the classic illustration of…

Cholera is caused by the bacterium Vibrio cholerae and spreads through water and food contaminated with faecal matter, which is why it breaks out after floods and wherever sewage mixes with the water supply; typhoid, hepatitis A, dysentery and polio spread the same way.

Soap is the sodium or potassium salt of a long chain fatty acid.

A moderator slows down the fast neutrons released by fission so that they can cause further fission, and heavy water is the best of them because it slows neutrons well while absorbing very few; in Indian pressurised heavy water reactors it also serves as the coolant that carries heat away…