STPM Physics 960 flashcards

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

SI base units

The seven fundamental units from which all others are derived: kilogram, metre, second, ampere, kelvin, mole and candela.

Dimensional homogeneity

A valid physical equation must have the same base dimensions on both sides; this allows checking equations and deriving relationships.

Fractional uncertainty rule

For a product or quotient, the fractional uncertainty of the result equals the sum of the fractional uncertainties of the individual quantities.

Random vs systematic error

Random errors scatter readings about a mean and are reduced by averaging; systematic errors shift all readings in one direction and are not reduced by averaging.

Equations of motion

For constant acceleration: v = u + at, s = ut + ½at², v² = u² + 2as, and s = ½(u + v)t.

Newton's second law

The net force on a body equals the rate of change of its momentum; for constant mass, F = ma.

Conservation of momentum

In the absence of external forces, the total linear momentum of a system remains constant before and after a collision or explosion.

Work-energy theorem

The net work done on an object equals its change in kinetic energy: W_net = ΔKE.

Centripetal acceleration

The acceleration of a body moving in a circle, directed towards the centre, with magnitude v²/r or rω².

Kepler's third law

The square of the orbital period of a planet is proportional to the cube of its mean distance from the Sun: T² ∝ r³.

Simple harmonic motion

Oscillatory motion in which acceleration is proportional to displacement from equilibrium and directed oppositely: a = −ω²x.

Critical damping

Damping that returns a system to equilibrium in the shortest time without overshooting or oscillating.

Ideal gas equation

The relationship pV = nRT = NkT, linking pressure, volume, amount of gas and absolute temperature.

First law of thermodynamics

The change in internal energy of a system equals the heat added to it minus the work done by it: ΔU = Q − W.

Root-mean-square speed

The square root of the mean of the squares of molecular speeds; for an ideal gas c_rms = √(3RT/M).

Carnot efficiency

The maximum possible efficiency of a heat engine operating between two reservoirs: η = 1 − T_C/T_H, with temperatures in kelvin.

Young's double-slit fringe spacing

The distance between adjacent bright fringes on a screen is y = λD/d, where D is slit-to-screen distance and d is slit separation.

Diffraction grating equation

Constructive interference maxima occur at angles satisfying d sin θ = nλ, where d is the grating spacing and n is the order.

Stationary wave on a string

A wave pattern with fixed nodes and antinodes; the fundamental frequency is f₁ = v/(2L) for a string fixed at both ends.

Doppler effect

The change in observed frequency when a source or observer moves relative to the medium; approaching raises frequency, receding lowers it.

Capacitance

The ratio of charge stored on a conductor to its potential: C = Q/V; unit farad (F).

Faraday's law of induction

The induced emf in a circuit is proportional to the rate of change of magnetic flux linkage: ε = −N dΦ/dt.

Kirchhoff's circuit laws

At any junction, the sum of currents entering equals the sum leaving; around any closed loop, the sum of emfs equals the sum of potential differences.

Magnetic flux density

The magnetic force per unit current per unit length on a conductor placed perpendicular to the field; unit tesla (T).

Zener diode

A diode designed to operate in reverse breakdown at a stable voltage, used for voltage regulation in circuits.

Transistor current gain

For a bipolar junction transistor, β = I_C/I_B, the ratio of collector current to base current in the active region.

Operational amplifier inverting gain

For an ideal op-amp in an inverting configuration, the voltage gain is −R_f/R_in, where R_f is feedback and R_in is input resistance.

De Morgan's theorems

Boolean identities: the complement of a product equals the sum of complements, and the complement of a sum equals the product of complements.

Photoelectric equation

Einstein's relation hf = Φ + K_max, where Φ is the work function and K_max is the maximum kinetic energy of emitted electrons.

de Broglie wavelength

The wavelength associated with a moving particle: λ = h/p = h/(mv), linking wave and particle properties.

Half-life

The time taken for half the nuclei in a radioactive sample to decay; related to decay constant by T₁/₂ = ln 2/λ.

Mass defect

The difference between the mass of a nucleus and the sum of the masses of its separate nucleons; converted to binding energy via E = Δmc².