NDA GK Questions 2026

Evaporation is the escape of molecules from a liquid surface into the air, and it slows as the air above fills with vapour; when the humidity falls the air can hold more vapour, so the rate of evaporation rises.

High clouds such as cirrus are thin and made of ice crystals; they let most of the sunlight pass through but absorb the outgoing infrared radiation from the surface, so their net effect is to warm.

In convection the heated matter itself moves and carries its energy with it: air near a warm surface expands, becomes lighter, rises as a current and is replaced by cooler air sinking in its place, and the same happens in a pan of boiling water.

An isotherm joins places of equal temperature, and on a world map the isotherms run roughly east to west, parallel to the latitudes, bending sharply where a continent meets an ocean because land and water heat at different rates.

Insolation measured at the top of the atmosphere is greatest over the equator, but what reaches the ground depends on cloud as well as on the angle of the rays, and the subtropical deserts lie under the descending limb of the Hadley circulation, where the sky is clear for most…

An inversion needs the ground to lose heat quickly and the air above to stay undisturbed: a long night gives time for terrestrial radiation to escape, a clear sky lets it escape, dry air absorbs little of it, and calm conditions keep the cold air lying in place, so the…

Advection is the sideways or horizontal transfer of heat by moving air, and in the middle latitudes most of the day to day variation in temperature comes from it; the hot loo that blows over north India in summer and the cold wave that follows a north-westerly wind in winter…

The orbit of the earth is an ellipse, so the distance from the sun changes through the year; the earth is closest at perihelion about the third of January and farthest at aphelion about the fourth of July, which is option D and the usual distractor in this question.

This is the normal lapse rate, the average fall of temperature with height in the troposphere, and it is the reason a hill station is cool while the plain at the same latitude is hot.

Of every hundred units of insolation arriving at the top of the atmosphere, about thirty-five are turned back before they can heat the ground, twenty-seven from the tops of clouds, two from snow and ice covered surfaces and the remainder scattered by the atmosphere; this reflected share is the albedo…

The word is a contraction of incoming solar radiation, and it means the short-wave energy from the sun that reaches the earth, measured in India by the India Meteorological Department in units of energy per unit area per unit time.

In uniform circular motion the magnitude of the velocity does not change, so the acceleration can have no component along the direction of motion; the whole of it is perpendicular to the velocity and points to the centre, which is why it is called centripetal, meaning centre seeking, and its…

To move along a curve a body needs a force directed towards the centre of that curve.

A shaft turning directly inside a sleeve slides against it, and sliding friction is large; placing hard steel balls between the shaft and its housing makes the surfaces roll over one another instead, and rolling friction is a small fraction of sliding friction, so less energy is wasted and the…

On a banked road the normal reaction is tilted, its vertical component balances the weight and its horizontal component supplies the centripetal force; dividing one equation by the other leaves the tangent of the banking angle equal to the square of the speed divided by the radius multiplied by the…

The angle of repose is the angle to which an inclined plane must be tilted before a body resting on it just begins to slide.

Distance is the length of the actual path and displacement is the straight line from the start to the finish, so on a curved path the two can never be equal: the arc of a circle is always longer than the chord joining its ends.

The centrifugal force has the same magnitude as the centripetal force, which for a body moving in a circle is the mass multiplied by the square of the angular velocity multiplied by the radius.

In uniform circular motion the body covers equal arcs in equal times, so its speed, a scalar, does not change; its kinetic energy and its angular velocity are constant too.

When a body rolls, the surfaces in contact change continuously and the irregularities have no time to interlock deeply, so rolling friction is very much smaller than sliding friction; this single fact is the reason the wheel was invented and the reason a ball bearing is fitted wherever a shaft…