PAF CAE / GDP Physics Master Guide Flashcards

A comprehensive vocabulary-style flashcard set covering F.Sc Part I and II Physics concepts, laws, and definitions as prescribed for PAF CAE and GDP academic tests.

Physical quantity

A quantity that can be measured and expressed in numbers, such as length, mass, and time.

Base (fundamental) quantities

Quantities that are independent of other quantities and are not defined in terms of them, including length, mass, time, temperature, electric current, luminous intensity, and amount of substance.

Precision

The degree of consistency and reproducibility of a measurement, related to least count and random error.

Accuracy

How close a measured value is to the true value, related to systematic error.

Significant figures

All digits in a measurement that are known reliably plus the first uncertain digit.

Dimensions of a quantity

The powers to which base quantities are raised to represent that quantity, for example $[Force] = [MLT^{-2}]$.

Principle of homogeneity of dimensions

The principle stating that dimensions on both sides of a valid physical equation must be the same.

Least count of Vernier callipers

$$0.01\,\text{cm}$$

Least count of Screw gauge (micrometer)

$$0.001\,\text{cm}$$

Scalar

A quantity with magnitude only, such as mass, time, speed, energy, and temperature.

Vector

A quantity with both magnitude and direction, such as displacement, velocity, force, momentum, and torque.

Unit vector

A vector of magnitude $1$ used to indicate direction only.

Resultant vector

The single vector that has the same effect as two or more vectors acting together.

Torque (moment of a force)

The turning effect of a force about a point or axis, defined as $\tau = r \times F$.

Equilibrium

A state in which the net force and net torque on a body are both zero.

First condition of equilibrium

The vector sum of all forces acting on a body is zero ($\Sigma F = 0$), meaning the body has no linear acceleration.

Second condition of equilibrium

The sum of all torques acting on a body about any point is zero ($\Sigma \tau = 0$), meaning the body has no angular acceleration.

Lami's theorem

For three coplanar, concurrent forces in equilibrium, each force is proportional to the sine of the angle between the other two.

Displacement

The change in position of a body; a vector quantity representing the shortest distance from initial to final position.

Impulse

The product of force and the time for which it acts ($J = F\Delta t$), equal to the change in momentum.

Projectile motion

The two-dimensional motion of a body under gravity alone after being given an initial velocity.

Newton's First Law (Law of Inertia)

A body remains at rest or in uniform motion in a straight line unless acted upon by a net external force.

Newton's Second Law

The rate of change of momentum is directly proportional to the applied force; expressed as $F = ma$.

Newton's Third Law

To every action there is an equal and opposite reaction.

Law of conservation of momentum

In the absence of an external force, the total momentum of a system remains constant.

Newton's law of gravitation

Every particle attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them: $F = \frac{Gm_{1}m_{2}}{r^{2}}$.

Work

Done when a force produces displacement in its own direction; $W = F \cdot d \cos(\theta)$.

Kinetic energy

Energy possessed by a body due to its motion; $KE = \frac{1}{2}mv^{2}$.

Potential energy (gravitational)

Energy possessed by a body due to its position or configuration; $PE = mgh$.

Escape velocity

The minimum velocity needed for a body to escape a planet's gravitational field permanently; $v_{e} = \sqrt{2gR}$.

Work-energy theorem

The net work done on a body equals the change in its kinetic energy.

Centripetal acceleration

The acceleration directed towards the centre of a circular path, responsible for changing the direction of velocity: $a_{c} = \frac{v^{2}}{r}$.

Moment of inertia

The rotational analogue of mass; a measure of a body's resistance to angular acceleration ($I = \Sigma mr^{2}$).

Angular momentum

The rotational analogue of linear momentum; defined as $L = I\omega = r \times p$.

Law of conservation of angular momentum

If no external torque acts on a system, its total angular momentum remains constant.

Viscosity

The internal friction of a fluid that resists relative motion between its layers.

Terminal velocity

The constant maximum velocity attained by a body falling through a viscous fluid when the net force on it becomes zero.

Reynolds number

A dimensionless number that predicts whether flow will be laminar or turbulent.

Equation of continuity

For an incompressible fluid in steady flow, $A_{1}v_{1} = A_{2}v_{2}$, meaning mass flow rate is constant.

Bernoulli's equation

For an ideal fluid in steady flow, $P + \frac{1}{2}\rho v^{2} + \rho gh = \text{constant}$; a statement of energy conservation for fluids.

Simple Harmonic Motion (SHM)

Oscillatory motion where acceleration is directly proportional to displacement from the mean position and always directed towards it.

Resonance

The phenomenon in which a system oscillates with maximum amplitude when driven at its natural frequency.

Hooke's law

Within the elastic limit, the restoring force of a spring is directly proportional to the extension: $F = -kx$.

Transverse wave

A wave in which particles vibrate perpendicular to the direction of wave propagation, such as light.

Longitudinal wave

A wave in which particles vibrate parallel to the direction of wave propagation, such as sound.

Doppler effect

The apparent change in frequency of a wave due to relative motion between source and observer.

Polarization

The phenomenon of restricting light vibrations to a single plane; proves light is a transverse wave.

Least distance of distinct vision

The closest distance ($25\,\text{cm}$ standard) at which the human eye can see clearly without strain.

Internal energy

The sum of the kinetic and potential energies of all the molecules of a gas.

First law of thermodynamics

The heat supplied to a system equals the increase in internal energy plus the work done by the system: $Q = \Delta U + W$.

Entropy

A measure of the disorder of a system; $\Delta S = \frac{\Delta Q}{T}$.

Electric flux

The measure of the number of electric field lines passing through a given surface.

Capacitance

The ability of a conductor to store charge per unit potential difference ($C = \frac{Q}{V}$).

Coulomb's Law

The force between two point charges is proportional to the product of charges and inversely proportional to the square of the distance: $F = \frac{1}{4\pi\epsilon_{0}} \frac{q_{1}q_{2}}{r^{2}}$.

Gauss's law

The total electric flux through a closed surface is equal to $\frac{1}{\epsilon_{0}}$ times the total charge enclosed.

Resistivity

A material property representing the resistance of a unit-length, unit-cross-section sample: $\rho = \frac{RA}{L}$.

Kirchhoff's current law (junction rule)

The algebraic sum of currents meeting at a junction is zero, representing charge conservation.

Kirchhoff's voltage law (loop rule)

The algebraic sum of EMFs and potential drops around any closed loop is zero, representing energy conservation.

Lenz's law

The direction of the induced current is always such that it opposes the change in flux that produced it.

RMS (root mean square) value

The value of steady DC that would produce the same heating effect as the given AC; $I_{rms} = \frac{I_{0}}{\sqrt{2}}$.

Photoelectric effect

The emission of electrons from a metal surface when light of sufficient frequency falls on it.

Work function

The minimum energy required to eject an electron from a metal surface.

de Broglie wavelength

The wavelength associated with a moving particle: $\lambda = \frac{h}{p}$.

Half-life

The time required for half the nuclei in a radioactive sample to decay.

Nuclear fission

The splitting of a heavy nucleus into two lighter nuclei, releasing a large amount of energy.

Nuclear fusion

The combining of two light nuclei into a heavier nucleus, releasing energy; powers the Sun.