IB Physics HL flashcards

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

SUVAT equation for v²

v² = u² + 2as. It relates final velocity, initial velocity, acceleration and displacement without needing time, and is valid only for constant acceleration.

Newton's second law

The net force on a body equals its rate of change of momentum: F_net = Δp/Δt. For constant mass this reduces to F = ma.

Elastic collision

A collision in which both momentum and total kinetic energy are conserved. No energy is converted to internal energy, deformation or sound.

Centripetal acceleration

The acceleration of an object moving in a circle at constant speed, directed toward the centre, with magnitude a = v²/r = ω²r.

Gravitational field strength

The gravitational force per unit mass at a point: g = F/m. Near a point mass g = GM/r², and it equals the local free-fall acceleration.

Orbital speed

For a circular orbit, the speed v = √(GM/r), where M is the mass of the central body and r is the orbital radius. It is independent of the orbiting mass.

Impulse

The product of force and the time for which it acts: J = FΔt. It equals the change in momentum and the area under a force–time graph.

Work–energy theorem

The net work done on an object equals its change in kinetic energy: W_net = ½mv² − ½mu². Work is Fs cos θ.

Ideal gas equation

pV = nRT = NkT, where R = 8.31 J/(mol·K) and k = 1.38 × 10⁻²³ J/K. Temperature must be in kelvin.

Kinetic theory result

The average translational kinetic energy of a gas molecule is (3/2)kT. It depends only on absolute temperature, not on the gas identity.

Root-mean-square speed

v_rms = √(3kT/m) = √(3RT/M). It gives a typical molecular speed; lighter molecules have higher v_rms at the same temperature.

First law of thermodynamics

ΔU = Q − W, where Q is heat added to the system and W is work done by the system. Internal energy changes when heat flows or work is done.

Specific latent heat

The energy per unit mass required to change the phase of a substance at constant temperature: Q = mL. No temperature change occurs during the phase change.

Isothermal process

A process at constant temperature. For an ideal gas, pV = constant, so pressure and volume are inversely proportional and internal energy does not change.

Simple harmonic motion

Oscillation in which acceleration is proportional to displacement and oppositely directed: a = −ω²x. Period T = 2π/ω, independent of amplitude.

Wave equation

v = fλ relates wave speed, frequency and wavelength. Frequency is set by the source; wavelength changes when the medium or wave speed changes.

Double-slit fringe spacing

For two slits separated by d, the spacing between adjacent maxima on a screen distance D away is Δy = λD/d, valid for small angles.

Diffraction grating equation

d sin θ = nλ gives the angle θ of the nth-order maximum, where d is the slit spacing. It produces sharper maxima than a double slit.

Standing wave nodes

Points of zero displacement in a standing wave. Adjacent nodes are separated by half a wavelength, and antinodes lie midway between nodes.

Doppler effect

The observed frequency of a wave changes when the source or observer moves relative to the medium. Approach increases frequency; recession decreases it.

Electric field strength

The electric force per unit positive charge: E = F/q. Near a point charge E = kQ/r², and in a uniform field E = V/d.

Electric potential

The work done per unit positive charge in bringing it from infinity to a point: V = kQ/r. It is a scalar, measured in volts.

Magnetic force on a charge

A charge q moving at speed v in a magnetic field B experiences F = qvB sin θ, perpendicular to both v and B. A stationary charge feels no magnetic force.

Magnetic flux

Φ = BA cos θ, the product of magnetic flux density and the area perpendicular to the field. The unit is the weber (Wb).

Faraday's law

The induced emf in a coil equals the negative rate of change of flux linkage: ε = −N ΔΦ/Δt. The minus sign reflects Lenz's law.

Motional emf

A conducting rod of length L moving at speed v perpendicular to a magnetic field B develops an emf ε = BvL, which can drive an induced current.

Half-life

The time for half the radioactive nuclei in a sample to decay. It relates to the decay constant by T½ = ln2/λ ≈ 0.693/λ.

Photoelectric work function

The minimum energy needed to remove an electron from a metal surface: φ = hf₀. It is a property of the metal, not of the incident light.

Maximum photoelectron kinetic energy

E_k,max = hf − φ. The maximum kinetic energy depends on photon frequency and the metal, not on the intensity of the incident light.

de Broglie wavelength

Every particle has a wavelength λ = h/p = h/(mv). It is significant only for small masses moving at low speeds, such as electrons.

Quantum tunnelling

A particle can pass through a potential barrier even when its energy is below the barrier height. The probability falls exponentially with barrier width and height.

IA data analysis criterion

Criterion D assesses whether data are processed correctly, uncertainties are propagated, and a graph or fit is used to derive a physically meaningful result.