NCEA Level 2 Physics flashcards
NCEA Level 2 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.
- Scalar vs vector
- A scalar has magnitude only, such as speed or mass. A vector has magnitude and direction, such as velocity, displacement, force or acceleration.
- Average velocity
- Average velocity equals total displacement divided by total time. It includes direction, so returning to the start gives zero average velocity even when distance travelled is nonzero.
- 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 energy
- In a closed system, total energy is conserved. Energy may transform between kinetic, potential, thermal and other forms, but the total amount remains constant.
- Momentum and impulse
- Momentum p = mv is mass times velocity. Impulse equals change in momentum, FΔt = Δp, and is the area under a force-time graph.
- Centripetal acceleration
- For uniform circular motion, acceleration points toward the circle's centre. Its magnitude is a_c = v²/r, where v is speed and r is radius.
- Projectile horizontal motion
- Without air resistance, a projectile's horizontal velocity stays constant because no horizontal force acts. Horizontal displacement equals horizontal velocity multiplied by time of flight.
- Torque in equilibrium
- Torque is force multiplied by perpendicular distance from the pivot, τ = Fd. An object is in rotational equilibrium when total clockwise torque equals total anticlockwise torque.
- Ohm's law
- For an ohmic conductor at constant temperature, voltage equals current times resistance, V = IR. Resistance is measured in ohms and equals V/I.
- Series circuit rules
- In a series circuit, the same current flows through every component. Voltages add to the supply voltage, and total resistance is the sum of individual resistances.
- Parallel circuit rules
- In a parallel circuit, each branch has the same voltage. Branch currents add to the total current, and total resistance is less than the smallest branch resistance.
- Electrical power
- Electrical power is the rate of energy transfer, P = VI = I²R = V²/R. Energy transferred is E = Pt, measured in joules when power is in watts and time in seconds.
- Resistivity formula
- Resistance of a uniform conductor is R = ρL/A. It increases with length L and resistivity ρ, and decreases as cross-sectional area A increases.
- Magnetic force on wire
- A current-carrying wire in a magnetic field can experience force F = BIL sinθ. The force is maximum when the wire is perpendicular to the field and zero when parallel.
- Lenz's law
- An induced current produces a magnetic field that opposes the change in magnetic flux causing it. This direction rule follows from conservation of energy.
- Ideal transformer
- For an ideal transformer, voltage ratio equals turns ratio: V_s/V_p = N_s/N_p. Power is conserved, so current ratio is inverse: I_s/I_p = N_p/N_s.
- Wave equation
- Wave speed equals frequency multiplied by wavelength, v = fλ. Frequency is the number of oscillations per second and wavelength is the distance between successive identical points.
- Transverse wave
- In a transverse wave, particles oscillate perpendicular to the direction of wave travel. Examples include waves on a string and electromagnetic waves.
- Longitudinal wave
- In a longitudinal wave, particles oscillate parallel to the direction of wave travel. Sound in air is longitudinal, forming compressions and rarefactions.
- Snell's law
- Snell's law relates incidence and refraction angles: n1 sinθ1 = n2 sinθ2. Refractive index n = c/v, where c is light speed in vacuum.
- Critical angle
- Total internal reflection can occur when light moves from a higher to a lower refractive index. The critical angle satisfies sinθ_c = n2/n1.
- Constructive interference
- Constructive interference occurs when waves meet in phase. For two sources, the path difference is a whole number of wavelengths, nλ, producing a maximum.
- Standing wave nodes
- Nodes are points of zero displacement in a standing wave. Adjacent nodes are separated by half a wavelength, λ/2, and antinodes lie midway between nodes.
- Electromagnetic spectrum order
- From longest to shortest wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. All electromagnetic waves travel at c in a vacuum.
- Atomic number and mass number
- Atomic number Z is the number of protons. Mass number A is protons plus neutrons. Isotopes have the same Z but different A.
- Photon energy
- A photon's energy is E = hf = hc/λ, where h is Planck's constant. Higher frequency or shorter wavelength means greater photon energy.
- Photoelectric threshold
- The photoelectric effect occurs when incident photon energy exceeds the metal's work function. Maximum kinetic energy of emitted electrons is E_k = hf − φ.
- Line emission spectrum
- A line emission spectrum contains bright wavelengths produced when electrons fall to lower energy levels. Each photon energy equals the difference between two atomic energy levels.
- Alpha decay
- Alpha decay emits a helium-4 nucleus, reducing mass number by four and atomic number by two. The parent nucleus changes into a different element.
- Half-life definition
- Half-life is the time for half the radioactive nuclei in a sample to decay. After n half-lives, the fraction remaining is (1/2)^n.
- Mass defect
- Mass defect is the difference between the mass of a nucleus and the sum of its separate nucleons. It equals the binding energy divided by c².
- Nuclear fission and fusion
- Fission splits a heavy nucleus into lighter nuclei; fusion joins light nuclei. Both release energy when the product has greater binding energy per nucleon.