RRB ALP GK Questions 2026

The Dutch scientist Huygens designed the first working pendulum clock in 1656, after Galileo had noticed that a swinging lamp took the same time for each swing whether it swung far or little, the property called isochronism.

In simple harmonic motion the acceleration equals minus omega squared times the displacement, so it grows with displacement and is greatest at the ends of the path, where its value is A omega squared and it points back towards the centre.

Potential energy is proportional to the square of the displacement, so it is greatest where the displacement is greatest, that is at the two ends of the path, where the body is momentarily at rest and its kinetic energy is zero.

The time period varies inversely as the square root of g, so if g falls to one sixth, the period is multiplied by the square root of six, about 2.45 times; the pendulum swings more slowly and a pendulum clock taken to the moon would lose time badly.

The time period varies as the square root of the length, so multiplying the length by four multiplies the period by the square root of four, that is by two; to double the period of a pendulum its length must be made four times.

A second's pendulum is one whose time period is exactly two seconds, so that each swing from one side to the other takes one second.

The time period of a simple pendulum is two pi times the square root of the length divided by g, in which the mass of the bob does not appear at all; a heavy bob and a light bob of the same length keep the same time, which is the…

A swing is a pendulum, and its speed is greatest at the lowest point, where all the potential energy gained at the top has turned into kinetic energy.

In simple harmonic motion the velocity is given by omega times the square root of A squared minus x squared.

Breaking stress is the greatest force per unit area that a substance can bear before it snaps, and since both the force and the area are already accounted for in the definition, what remains is a constant of the substance itself, the same for a thin wire and a thick…

The two strips are joined and carry the load together, so they suffer the same strain. Since stress equals the modulus multiplied by the strain, the stress in steel is three times the stress in aluminium.

When the block is released suddenly it falls freely at first, so at the lowest point its speed is zero and all the gravitational potential energy it has lost has gone into the spring.

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.