33 of the Physics glossary’s terms, each with the part of the syllabus where you first meet it.
The frequency at which a system oscillates when displaced and left to oscillate freely, with no driving force.
A huge cloud of gas, mostly hydrogen and helium, and dust in space, in which stars form.
A process in which a change causes effects that reduce the original change, such as a warmer surface radiating more energy away.
A point where the fields of two or more bodies cancel, so the resultant field strength is zero.
A neutral particle of almost zero mass that interacts extremely weakly with matter; emitted with the positron in β⁺ decay.
The number of neutrons in a nucleus, .
The extremely dense remnant core of a massive star after a supernova, about 20 km across, made mostly of neutrons and supported by the pressure of the closely packed neutrons.
Fission that happens after a heavy nucleus, such as uranium-235, absorbs a neutron and becomes highly unstable.
The ratio of the numbers of neutrons and protons in a nucleus; stable nuclei have values from about 1 (light) to about 1.5 (heavy).
The SI unit of force: the resultant force that gives a mass of 1 kg an acceleration of , so .
A body stays at rest or moves with constant velocity in a straight line unless a resultant external force acts on it.
Every point mass attracts every other with a force proportional to the product of the masses and inversely proportional to the square of their separation: .
The resultant force on a body equals its rate of change of momentum, ; for constant mass, .
The resultant torque on a rigid body equals its moment of inertia multiplied by its angular acceleration, .
When body A exerts a force on body B, B exerts a force of the same type on A that is equal in size and opposite in direction.
A point on a standing wave where the displacement is always zero. Adjacent nodes are half a wavelength apart.
A force, such as friction or fluid resistance, whose work depends on the path taken and which transfers mechanical energy to internal energy.
A component whose resistance changes with the current or pd, such as a filament lamp or an LED.
A line drawn perpendicular to a surface or boundary at the point where a ray meets it. Angles of incidence, reflection and refraction are measured from it.
The component of the contact force between two surfaces that is perpendicular to them, .
The mass of a nucleus divided by its volume; about , the same for all nuclei.
One of the discrete energies a nucleus can have; transitions between them give γ photons and α particles of definite energies.
The splitting of a heavy nucleus into two smaller nuclei of comparable mass, usually with the release of two or three neutrons and energy.
The joining of two light nuclei to form a heavier nucleus, which releases energy when the product has a higher binding energy per nucleon.
Rutherford's model of the atom (1911): a tiny, massive, positive nucleus surrounded by electrons in mostly empty space.
The symbol for a nuclide, where X is the chemical symbol, the proton number and the nucleon number.
The radius of a nucleus, given by with
A device in which a controlled, self-sustaining fission chain reaction releases energy at a steady rate.
A particle in the nucleus: a proton or a neutron.
The total number of protons and neutrons in a nucleus.
The formation of chemical elements by nuclear reactions, mainly fusion in stars and reactions in supernovae.
The small, dense, positively charged centre of an atom, made of protons and neutrons, which holds nearly all of the atom's mass in a region about to m across.
A particular kind of nucleus, with a definite number of protons and neutrons, written .