physics key words

instantaneous speed

speed of an object at any given time

Absolute scale of temperature

A scale for temperature based on absolute zero and the triple point of pure water

absolute zero

The lowest possible temperature, the temperature at which substances have minimum internal energy

Acceleration of free fall

The rate of change of velocity of an object falling through a gravitational field

air resistace

The drag or resistive forces experienced by an object moving through air

Amount of substance

A measure of the amount of matter in moles

angular frequency

ω = 2πf

angular velocity

The rate of change of angle for an object moving in a circle

Aphelion

Furthest point from sun in an orbit

Archimedes' Principle

The upthrust on an object in a fluid is equal to the weight of fluid it displaces

arcminute

A minute of an arc, 1° = 60 arc minutes

arcsecond

A second of an arc, 1 arc minute= 60 arcseconds

Astronomical Unit (AU)

The average distance between the earth and the sun: 1

Avogadro constant

The number of atoms in 0

Big Bang Theory

All matter in the universe was contained in a singularity, the beginning of space and time that rapidly expanded outwards

Black body

An idealised object that absorbs all EM radiation incident on it, when its in thermal equilibrium, it emits a characteristic distribution of wavelengths at a specific temperature

Blackhole

The remenant core of a massive star after it has undergone supernovas, core has collapsed so far it would need an escape velocity greater than the speed of light, nothing can escape

Blueshift

Shortening of observed wavelength that occurs when the wave source is moving towards the observer

Boltzmann constant

The molar gas constant R, divided by Avogadro's constant, constant that relates mean kinetic energy of atoms or molecules in a gas to temperature

Boyle's law

The pressure of an ideal gas is inversely proportional to it's volume, provided that the mass of gas and temperature do not vary

breaking strength

The stress value at the point of fracture, calculated by dividing breaking goals force by cross sectional area

brittle

Property of a material that does not show plastic deformation and deforms very little (if at all) under high stress

Brownian motion

The continuous random motion of small particles suspended in a fluid, visible under a microscope

centripetal acceleration

The acceleration of any object travelling in a circular path at constant speed, which always acts towards the centre of the circle

centripetal force

A force that keeps an object moving with constant speed in a circular path

Chandrasekhar limit

The mass of a stars core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse, 1

Compression

The decrease in length of an object when a compressive force is applied to it

Compressive deofrmation

A change in shape of an object due to compressive forces

continuous spectrum

A spectrum in which all visible frequencies or wavelengths are present (produced by a heated filament lamp)

Cosmological Principle

The assumption that, when viewed on a large scale the universe is homogenous and isotropic and the laws of physics are universal

Damping

An oscillation is damped when an external force that acts on the oscillator has the effect of reducing the amplitude of its oscillations

Doppler effect

The change in frequency and wavelength of the waves received from an object moving relative to an observer compared to what would be observed without the relative motion

driving frequency

The frequency with which the periodic driver force is applied to a system in forced oscillation

ductile

Property of a material that has a large plastic region in stress-strain graph, so can be drawn into wires

eccentricity

A measure of elongation of an ellipse

elastic deformation

A reversible change in the shape of an object due to compressive or tensile forces, removal of force means object will return to its original shape and size

elastic limit

The value of stress of force beyond which elastic deformation becomes plastic deformation, and the material will no longer return to it's original shape and size when the stress or force is removed

elastic potential energy

The energy stored in an object because of its deformation

electron degeneracy pressure

A quantum-mechanical pressure created by the electrons in the core of a collapsing star due to the Pauli exclusion principle

emission line spectrum

A set of specific frequencies of EM radiation, visible as bright lines in spectroscopy, emitted by excited atoms as their electrons make transitions between higher and lower energy states, losing the corresponding amount of energy in the form of photons

energy level

A discrete (quantised) amount of energy that an electron within an atom is permitted to possess

Equilibrium

A body is in equilibrium when the net force ans net moment acting on it are 0

escape velocity

The minimum velocity at which an object has just enough energy to leave a specified gravitational field

Excited

An atom containing an electron that has absorbed some energy and been boosted to a higher energy level

Expanding Universe

The idea that the fabric of space and time is expanding in all directions and that as a result any point is moving away from every other point in the universe

Forced oscillation

An oscillation in which a periodic driver force is applied to the oscillator

Free oscillation

The motion of a mechanical system displaced from its equilibrium position and then allowed to oscillate without any external forces

Frequency

The number of wavelengths passing a given point per unit time

fundamental frequency

The lowest frequency at which an object can vibrate

gas pressure

The pressure of the nuclei in a stars core pushing outwards and counteracting the gravitational force pulling matter in the star inwards

Geostationary sateliite

A satellite that remains in the same position relative to a spot on the earths surface, by orbiting in the direction of the earths rotation over the equator with a period of 24 hours

Gravitational field

A field created around any object with mass, extending all the way to infinity, but diminishing as the distance from the centre of mass increases

Gravitational field strength

The gravitational force entered per unit mass at a point within a gravitational field

gravitational potential

The work done per unit mass to bring an object from infinity to that point in a gravitational field

gravitational potential energy

The capacity for doing work as a result of an object's position in a gravitational field

ground state

The energy level with the most negative value possible for an electron within an electron, the most stable state of an electron

Heavy Damping

Damping that's occurs when the damping forces are large and the period of oscillation increases slightly with a rapid decrease in amplitude

Homogenous

The universe is uniformly distributed when viewed on a sufficiently large scale

Hooke's Law

The force applied is directly proportional to the extension of the spring unless the limit of proportionality is exceeded

Hubble's Law

The recessional velocity is directly proportional to the distance from earth

Hubble's constant, H0

The gradient of the line of best fit of recessional speed against distance from earth of other galaxies

hysteresis loop

A loop-shaped plot obtained when loading and unloading a material produce different deformations

Impulse

The area under a force-time graph, product of force and the time for which it acts

inelastic collision

A collision in which kinetic energy is transferred to other forms (not conserved)

Inflation

A phase of astonishing acceleration of the expansion of the universe, t= 10^-35 seconds after big bang

Internal energy

The sum of the random distribution of kinetic and potential energy of molecules or atoms within a substance

Isochronous oscillator

An oscillator that has the same period regardless of amplitude

Isotherm

A line on a pressure-volume graph that connects points at the same temperature

Isotropic

The universe is the same in all directions to any observer

Kepler's first law of planetary motion

The orbit of a planet is an ellipse with the sun at one of the two foci

Kepler's second law of planetary motion

A line segment connecting a planet to the sun sweeps out equal areas during equal intervals of time

Kepler's third law of planetary motion

The square of the orbital period T of a planet is directly proportional to the cube of its average distance r from the sun

kilo-watt hour

1kWh= 3

Light damping

Damping that occurs when the damping forces are small and the period of oscillations are almost unchanged