NCEA Level 3 Physics flashcards
NCEA Level 3 Physics · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Newton's second law
- The net force on an object equals its mass times acceleration, F_net = ma. The acceleration is in the same direction as the net force.
- Conservation of momentum
- In the absence of external net forces, the total momentum of a system remains constant. This applies to collisions and explosions in one or two dimensions.
- Centripetal acceleration
- For an object moving in a circle of radius r at speed v, the centripetal acceleration is a = v²/r, directed toward the centre of the circle.
- Simple harmonic motion
- Oscillating motion where acceleration is proportional and opposite to displacement, a = −ω²x. The period is independent of amplitude for ideal SHM.
- Period of a pendulum
- For a simple pendulum of length l in small oscillations, the period is T = 2π√(l/g), independent of the mass of the bob.
- Impulse
- Impulse equals the change in momentum, J = FΔt = Δp. It is the area under a force–time graph and has units of newton-seconds.
- Projectile motion
- Motion under gravity where horizontal and vertical components are independent. Horizontal velocity is constant; vertical acceleration is g downward.
- Rotational kinetic energy
- The kinetic energy of a rotating body is E = ½Iω², where I is the moment of inertia about the axis and ω is the angular velocity.
- Work–energy theorem
- The net work done on an object equals its change in kinetic energy: W_net = ΔKE. Work is calculated as W = Fd cos θ.
- Torque
- Torque is the turning effect of a force about an axis, τ = rF sin θ, where r is the distance from the pivot and θ is the angle between force and lever arm.
- Wave equation
- The speed of a wave equals its frequency multiplied by its wavelength, v = fλ. Frequency is set by the source and remains constant across media.
- Constructive interference
- When two coherent waves meet in phase, their displacements add to give a larger amplitude. Path difference equals a whole number of wavelengths, nλ.
- Diffraction grating equation
- For a grating with slit spacing d, maxima occur at angles given by d sin θ = nλ, where n is the order of the maximum.
- Standing wave on a string
- A standing wave forms when two waves of equal frequency travel in opposite directions. The fundamental frequency is f₁ = v/(2L), with harmonics at integer multiples.
- Doppler effect
- The observed frequency of a wave changes when the source or observer moves relative to the medium. Approaching motion raises frequency; receding motion lowers it.
- Snell's law
- When light crosses a boundary between media, n₁ sin θ₁ = n₂ sin θ₂, where n is the refractive index and angles are measured from the normal.
- Total internal reflection
- Occurs when light travels from a denser to a less dense medium at an angle greater than the critical angle, sin θ_c = n₂/n₁, and is fully reflected.
- Refractive index
- The refractive index of a medium is the ratio of the speed of light in vacuum to its speed in the medium, n = c/v. It is always at least 1.
- Ohm's law
- The current through a conductor is proportional to the potential difference across it, V = IR, provided temperature remains constant.
- Parallel resistance
- For resistors in parallel, the reciprocal of total resistance equals the sum of reciprocals: 1/R_total = 1/R₁ + 1/R₂ + … The total is less than the smallest resistor.
- Electrical power
- Power dissipated in a component is P = VI = I²R = V²/R. It represents the rate at which electrical energy is converted to other forms.
- Kirchhoff's voltage law
- The sum of potential differences around any closed loop in a circuit is zero, reflecting conservation of energy.
- Capacitor energy
- The energy stored in a charged capacitor is E = ½CV² = ½QV, where C is capacitance, V is voltage, and Q is charge.
- Faraday's law
- The induced EMF in a coil equals the negative rate of change of magnetic flux linkage: EMF = −N ΔΦ/Δt.
- Lenz's law
- The direction of an induced current is such that it opposes the change in magnetic flux that produced it, consistent with conservation of energy.
- Magnetic force on a wire
- A current-carrying wire in a magnetic field experiences a force F = BIL sin θ, where θ is the angle between the wire and the field.
- Photoelectric effect
- Light of sufficient frequency ejects electrons from a metal surface. Maximum kinetic energy is K_max = hf − φ, where φ is the work function.
- Photon energy
- The energy of a photon is E = hf = hc/λ, where h is Planck's constant and f is the frequency of the electromagnetic radiation.
- de Broglie wavelength
- Particles have an associated wavelength λ = h/p = h/(mv), where p is momentum. This wave nature is observable for small particles such as electrons.
- Half-life
- The time taken for half the nuclei in a radioactive sample to decay. After n half-lives, the fraction remaining is (½)^n.
- Radioactive decay law
- The number of undecayed nuclei decreases exponentially: N = N₀e^(−λt), where λ is the decay constant related to half-life by λ = ln 2 / T_½.
- Mass–energy equivalence
- Mass and energy are equivalent through E = mc². In nuclear reactions, the mass defect appears as released energy, explaining fission and fusion energy.