Tamil Nadu HSE First Year Physics flashcards

35 cards. Read the term and the definition here. The deck at the top of this page is optional.

Dimensional formula of force

Force equals mass times acceleration, so its dimensional formula is [M L T^-2]. This follows from Newton's second law and is used to check the homogeneity of mechanical equations.

Principle of homogeneity

In a correct physical equation, every term on both sides must have identical dimensions. It verifies the form of an equation but cannot determine numerical constants such as 2 or pi.

Vernier least count

Least count equals one main scale division minus one vernier scale division. If n vernier divisions equal n-1 main divisions, the least count is one main division divided by n.

Propagation of errors in product

When a result is the product or quotient of measured quantities, the fractional errors add. For Z equal to A times B, the fractional error in Z is the sum of those in A and B.

Equations of uniformly accelerated motion

For constant acceleration: v equals u plus at, s equals ut plus half at squared, and v squared equals u squared plus 2as. These fail when acceleration changes with time.

Projectile horizontal range

For projection speed u at angle theta, range R equals u squared times sin 2 theta divided by g. Range is maximum at 45 degrees and equal for complementary angles.

Relative velocity

The velocity of A as observed from B is the vector difference of their velocities. For motion in one direction, relative speed is the difference of speeds.

Radial acceleration

A body moving on a circle of radius r at speed v has centripetal acceleration v squared divided by r, directed towards the centre. It changes direction, not speed.

Newton's second law

The net external force on a body equals the rate of change of its momentum. For constant mass this reduces to force equals mass times acceleration.

Limiting friction

The maximum static friction before sliding begins equals the coefficient of static friction times the normal reaction. Once sliding starts, kinetic friction is smaller and roughly constant.

Angle of repose

The steepest incline angle at which a block remains at rest. Its tangent equals the coefficient of static friction between block and plane.

Banking of roads

On a frictionless banked curve of radius r at angle theta, the safe speed satisfies v squared equals rg tan theta. Banking supplies the centripetal force through the normal reaction.

Work-energy theorem

The net work done by all forces on a body equals its change in kinetic energy. It holds even when forces vary, provided net work is computed correctly.

Coefficient of restitution

Ratio of relative speed of separation to relative speed of approach along the line of impact. It is one for elastic and zero for perfectly inelastic collisions.

Conservation of mechanical energy

When only conservative forces do work, the sum of kinetic and potential energy stays constant. Friction reduces this total by the work done against it.

Centre of mass

The point where the mass-weighted position vectors of all particles average out. The centre of mass moves as if the total external force acted there.

Parallel-axis theorem

Moment of inertia about any axis equals that about a parallel axis through the centre of mass plus mass times the square of the separation between the axes.

Angular momentum conservation

If no external torque acts, total angular momentum stays constant. A skater pulling in the arms reduces moment of inertia and so spins faster.

Rolling kinetic energy

A rolling body has translational plus rotational energy. Total kinetic energy equals half mass times speed squared times one plus moment of inertia over mass radius squared.

Escape velocity

Minimum speed needed to leave Earth's gravity without further propulsion. It equals the square root of 2gR, about 11.2 km per second, independent of the body's mass.

Variation of g with depth

Inside the Earth at depth d, acceleration due to gravity is g times one minus d over R. It decreases linearly and becomes zero at the centre.

Kepler's third law

The square of a planet's orbital period is proportional to the cube of the semi-major axis of its orbit. The constant depends on the mass of the central body.

Young's modulus

Ratio of longitudinal stress to longitudinal strain within the elastic limit. It measures stiffness: a larger value means the material stretches less for the same stress.

Excess pressure in a soap bubble

Inside a soap bubble the pressure exceeds the outside value by four times surface tension divided by radius. A liquid drop has half that excess because it has one surface.

Terminal velocity

The constant speed reached when viscous drag plus buoyancy balances weight. For a sphere it grows with the square of radius and inversely with fluid viscosity.

Bernoulli's theorem

For steady, non-viscous, incompressible flow, pressure plus kinetic energy density plus gravitational energy density is constant along a streamline. It explains lift and carburettor action.

First law of thermodynamics

Heat supplied to a system equals the increase in internal energy plus the work done by the system. It is the energy conservation statement for thermal processes.

Carnot efficiency

The maximum efficiency of any engine working between two reservoirs is one minus the ratio of sink to source temperature in kelvin. No real engine can exceed it.

Adiabatic process relation

In a reversible adiabatic process, pressure times volume raised to gamma stays constant. Gamma is the ratio of specific heats of the gas.

RMS molecular speed

The square root of the mean of squared molecular speeds equals the square root of three RT divided by molar mass. It rises with the square root of temperature.

Equipartition of energy

Each quadratic degree of freedom of a molecule carries average energy of half kT in thermal equilibrium. This gives three halves kT for a monatomic gas.

Simple pendulum period

For small oscillations the period is two pi times the square root of length divided by acceleration due to gravity. It is independent of the bob mass.

Beat frequency

When two waves of nearly equal frequency superpose, the loudness rises and falls. The number of beats per second equals the difference of the two frequencies.

Closed pipe harmonics

A pipe closed at one end supports only odd harmonics, with fundamental frequency v divided by four times length. An open pipe supports all harmonics.

Screw gauge least count

Least count equals pitch divided by the number of circular scale divisions. Pitch is the linear distance moved in one full rotation of the screw.