LC Physics flashcards

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

Acceleration

The rate of change of velocity with respect to time; it is a vector quantity measured in metres per second squared (m/s²).

Newton's second law

The net force on an object equals its mass multiplied by its acceleration (F = ma); force and acceleration are in the same direction.

Conservation of momentum

In a closed system with no external forces, the total momentum before a collision or explosion equals the total momentum after it.

Moment of a force

The turning effect of a force about a pivot, calculated as force multiplied by the perpendicular distance from the pivot to the line of action.

Centripetal acceleration

The acceleration of an object moving in a circle at constant speed, directed toward the centre; its magnitude is v²/r.

Hooke's law

The extension of an elastic object is directly proportional to the applied force, provided the limit of proportionality is not exceeded; F = kx.

Gravitational potential energy

The energy stored by an object due to its position in a gravitational field; near Earth it is calculated as mgh.

Frequency

The number of complete oscillations or cycles of a wave per second; it is measured in hertz (Hz) and equals 1/T.

Refractive index

The ratio of the speed of light in vacuum to the speed of light in a medium; also equal to sin i / sin r for light crossing a boundary.

Critical angle

The angle of incidence in the denser medium for which the refracted ray travels along the boundary; total internal reflection occurs above it.

Constructive interference

The superposition of two coherent waves in phase, producing a resultant wave of greater amplitude; path difference is a whole number of wavelengths.

Diffraction

The spreading of waves when they pass through a gap or around an obstacle; it is most noticeable when the gap is similar to the wavelength.

Doppler effect

The change in observed frequency of a wave when the source and observer move relative to each other; approaching motion raises frequency.

Coulomb's law

The electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation.

Electric field strength

The force per unit positive charge at a point in an electric field; measured in newtons per coulomb (N/C) or volts per metre.

Ohm's law

For a conductor at constant temperature, the current is directly proportional to the potential difference across it; V = IR.

Resistance

The opposition of a conductor to electric current, defined as the ratio of potential difference across it to the current through it; measured in ohms.

Capacitance

The ability of a capacitor to store charge per unit potential difference; C = Q/V and is measured in farads (F).

Faraday's law

The induced emf in a circuit is proportional to the rate of change of magnetic flux through the circuit; direction is given by Lenz's law.

Root mean square voltage

The equivalent steady DC voltage that would produce the same heating effect in a resistor; for a sine wave it equals peak voltage divided by √2.

Photon

A quantum of electromagnetic radiation carrying energy E = hf, where h is Planck's constant and f is the frequency.

Work function

The minimum energy required to remove an electron from the surface of a metal; it determines the threshold frequency for the photoelectric effect.

Threshold frequency

The minimum frequency of incident light that can cause photoelectric emission from a given metal surface; below it no electrons are emitted.

de Broglie wavelength

The wavelength associated with a moving particle, given by λ = h/p, where p is the particle's momentum.

Half-life

The time required for half of the radioactive nuclei in a sample to decay; it is constant for a given isotope and independent of sample size.

Mass defect

The difference between the mass of a nucleus and the sum of the masses of its separate nucleons; it is equivalent to the binding energy via E = mc².

Specific heat capacity

The energy required to raise the temperature of 1 kg of a substance by 1 K; measured in joules per kilogram per kelvin.

Specific latent heat

The energy required to change 1 kg of a substance from one phase to another without a change in temperature; measured in J/kg.

Thermal equilibrium

The state in which two objects in contact have the same temperature, so there is no net transfer of heat between them.

Conduction

The transfer of heat through a material by collisions between particles, without bulk movement of the material; metals are good conductors.

Convection

The transfer of heat in fluids by the movement of warmer, less dense fluid rising and cooler, denser fluid sinking.

Absolute zero

The lowest possible temperature, 0 K or −273.15 °C, at which particles have minimum kinetic energy.