NDA GK Questions 2026

Once a ductile specimen passes its ultimate tensile strength, the deformation stops being uniform and concentrates in one short length, which draws out into a narrow waist.

The restoring force grows from zero to its final value as the wire is stretched, so the work done is the average force multiplied by the extension, and dividing by the volume of the wire leaves half the product of stress and strain as the energy stored in each unit…

When a wire is pulled it lengthens and at the same time grows thinner, and Poisson's ratio records how large the sideways contraction is compared with the lengthwise extension; it is a pure number, with theoretical limits of minus one and one half and practical values of about 0.2 to…

Elasticity in physics is not the ability to stretch far but the strength of the restoring tendency, measured by the stress needed to produce a given strain, and steel demands an enormously greater stress than rubber for the same fractional extension.

The bulk modulus measures how strongly a substance resists a change in volume under uniform pressure, so its reciprocal measures how readily the volume yields, and that quantity is called compressibility.

It governs the stretching or compression of a wire or rod along its length and is obtained by dividing the force per unit area of cross section by the fractional change in length.

Strain is defined as the change in a dimension divided by the original value of the same dimension, a length divided by a length or a volume divided by a volume, so the units cancel and only a pure number survives.

Stress is the restoring force divided by the area over which it acts, so its unit is the newton per square metre, and that combination is given the special name pascal, the same unit used for pressure.

Hooke found that so long as a body is not strained beyond its elastic limit, the restoring force per unit area rises in step with the fractional deformation, and the constant ratio of the two is called the modulus of elasticity.

Glycolysis spends two molecules of ATP in the preparatory steps that phosphorylate glucose and fructose, and produces four by substrate level phosphorylation in the later steps, so the net gain is two ATP along with two molecules of reduced NAD.

Sugar is actively loaded into the sieve tubes at the source, water follows from the xylem by osmosis and raises the pressure there, and the resulting gradient pushes the whole solution to the sink, where sugar is unloaded and water returns to the xylem.

In yeast the pyruvic acid formed by glycolysis is decarboxylated and then reduced to ethyl alcohol, a process called alcoholic fermentation, which is the basis of brewing and of the rising of dough.

The respiratory quotient is the volume of carbon dioxide released divided by the volume of oxygen used. When glucose is oxidised completely, six molecules of oxygen are used and six of carbon dioxide are released, so the ratio is one.

Pyruvic acid formed in glycolysis enters the mitochondrion, is converted to acetyl coenzyme A and is oxidised completely in the matrix through the cycle named after Hans Krebs, who received the Nobel Prize for the discovery; the cycle releases carbon dioxide and reduced coenzymes.

Glycolysis, also called the Embden Meyerhof Parnas pathway, splits one molecule of glucose into two molecules of pyruvic acid in the cytoplasm, needs no oxygen and gives a net gain of two ATP along with two molecules of reduced NAD.

Ganong's potometer and the simpler bubble potometer measure the water absorbed by a cut shoot in a given time, and since almost all of that water is lost as vapour, the reading is taken as the rate of transpiration.

In light, potassium ions are actively pumped into the guard cells, their solute concentration rises, water enters by osmosis, the cells swell and because their inner walls are thicker they bend apart, opening the pore; when potassium leaves, the cells lose water and the pore closes.

Its sieve tubes, helped by companion cells, carry sucrose and other soluble food from a source such as a mature leaf to a sink such as a root, fruit or bud, and the movement can be upward or downward.

It occurs through pores called hydathodes at the leaf margin or tip, usually in the early morning when the soil is moist, the air is humid and transpiration is low, so root pressure forces out drops of water with dissolved salts; Colocasia, grasses and tomato show it well.

Dixon and Joly explained that water molecules cling to one another by cohesion and to the xylem walls by adhesion, forming an unbroken column; evaporation from the leaf surface creates a suction at the top that pulls this column upward.