Definitons For Paper 1 Flashcards
Acceleration
The rate of change of velocity
Acceleration of free fall
The rate of change of velocity of an object falling in a gravitational field
Air resistance
The drag or resistive force experienced by objects moving through air
Antiparallel
In the same line but opposite directions
Archimedes’ principle
The upthrust of an object in a fluid is equal to the weight of fluid it displaces
Average speed
The rate of change in distance calculated over a complete journey
Average velocity
Th changes in displacement for a journey divided by the time taken
Braking distance
Distance travelled by a vehicle from the time the brakes are applied until the vehicle stops
Breaking strength
The stress value at the point of fracture, calculated by dividing the breaking force by the cross-sectional area
Brittle
Property of a material that does not show plastic deformation and deforms very little under high stress
Centre of gravity
An imaginary point at which the entire weight of an object appears to act
Centre of mass
A point through which any externally applied force produces straight-line motion but no rotation
Closed system
An isolated system that has no interaction with its surroundings
Component
One of the two perpendicular vectors obtained by resolving a vector
Compression
The decrease in length of an object when a compressive force is exerted on it
Compressive deformation
A change in shape of an object due to compressive forces
Constant speed
Motion in which the distance travelled per unit time stays the same
Constant velocity
Motion in which the change in displacement per unit time stays the same e
Couple
A pair of equal and opposite forces acting on a body but not in the same straight line
Density
The mass per unit volume of a substance
Displacement
The distance travelled in a particular direction
Drag force
The resistive fore exerted by a fluid in an object moving through it
Ductile
Property of a material that has a large plastic region in a stress-strain graph
Efficiency
The ratio of useful output energy to total input energy
Elastic deformation
A reversible change in the shape of an object due to a compressive or tensile force - removal of stress of force will return the object to its original shape and size
Elastic limit
The value of stress and force beyond which elastic deformation becomes plastic deformation, and the material or object will no longer return to its original shape and size when the stress or force is removed
Elastic potential energy
The energy stored in an object because of its deformation
Energy
The capacity for doing work measured in joules
Equilibrium
When the net force and net moment acting on a body is zero
Extension
The increase in length of an object when a tensile force is exerted on it
Fluid
A substance that can flow, including liquids and gases
Force
A push or pull on an object measured in newtons
Force constant
A quantity determined by dividing force by extension for an object obeying Hookes’ law - constant of proportionality k
Force-extension graph
Graph of force against extension with the area under the graph equal to the work done on the material
Force-time graph
A graph of net force against time, area under the graph equal to the impulse
Free fall
The motion of an object accelerating under gravity with no other force acting on it
Gravitational potential energy
The capacity for doing work as a result of an object’s position in a gravatational field
Hooke’s law
The force applied is directly proportional to the extension of the spring unless the limit of proportionality is exceeded
Hysteresis loop
A loop-shaped plot obtained when loading and unloading a material produce different deformations
Impulse
The area under a force-time graph - the product of force and time for which the force acts
Inelastic collision
A collision in which kinetic energy is lost
Instantaneous speed
The speed at the moment it is measured
Kinetic energy
The energy associated with an object as a result of its motion
Limit of proportionality
The value of stress or force beyond which stress is no longer directly proportional to strain
Linear momentum
A property of an object travelling in a straight line - product of its mass and velocity
Mass
Amount of matter - base quantity is kilograms
Moment
The product of force and perpendicular distance from a pivot
Newtons first law of notion
A body will remain at rest or continue to move with constant velocity unless acted upon by a resultant force
Newton’s second law of motion
The rate of change in momentum of an object is directly proportional to the resultant force and takes place in the direction of the force
Newton’s third law of motion
When two objects interact, each exerts an equal but opposite force on the other during the interaction
Normal contact force
The force exerted by a surface on an object which acts perpendicularly to the surface
Perfectly elastic collision
A collision in which no kinetic energy is lost
Plastic deformation
An irreversible change in the shape of an object sue to a compressive or tensile force - removal of stress or force produces permanent deformation
Plumb-line
A string with a weight used to provide a vertical reference line
Power
The rate of work done measured in watts
Pressure
The force exerted per unit cross-sectional area measured in pascals
Principle of conservation of energy
The total energy of a system remains constant - energy cannot be created nor can it be destroyed
Principle of moments
For a body in rotational equilibrium the sum of anticlockwise moments about a point is equal to the sum of clockwise moments about the same point
Projectile
An object that us throw or propelled on the surface of the earth
Restoring force
A force that tries to return a system to its equilibrium position
Resultant vector
A single vector that has the same effect as two or more vectors added together
Scalar quantity
A quantity with magnitude but no direction
Stiffness
The ability of an object to resist deformation
Stopping distance
The total distance travelled from the time when a driver first sees a reason to stop to the time when the vehicle stops the sum of thinking and braking distances
Strong material
Large value for ultimate tensile strength
Tensile deformtaion
A change in the shape of an object due to tensile forces
Tensile force
Equal and opposite forces acting on a material to stretch it
Tensile strain
The extension per unit length
Tensile stress
The force per unit cross-sectional area
Tension
The pulling force exerted by a string, cable or chain on an object
Terminal velocity
The constant speed reached by an object when the drag force is equal and opposite to the weight of the object
Thinking distance
The distance travelled by a vehicle from when the driver first perceives a need to stop to when the brakes are applied
Time of flight
Time taken for an object to complete its motion
Torque of a couple
The product of one of the force of a couple and the perpendicular distance between the forces
Ultimate tensile strength
The maximum stress that a material can withstand before it breaks
Uniform gravitational field
A gravitational field in which the field lines are parallel and the value for g remains constant
Upthrust
The upward buoyant force exerted on a body immersed in a fluid
Velocity
A vector quantity equal to the rate of change in displacement
Weight
The gravitational force on an object measured in newtons
Work
The product of force and the distance moved in the direction of the force measured in joules
Yield point
A point on a stress-strain graph beyond which the deformation is no longer entirely elastic
Absolute scale of temperature
A scale for measuring temperature based on absolute zero and the triple point of pure water - increments are equal to those of the Celsius scale = Kelvin scale
Absolute zero
The lowest possible temperature, the temperature at which substances have minimum internal energy
Amount of substance
A measure of the amount of matter in moles
Angular frequency
A quantity used in oscillatory motion - equal to the product of frequency and 2π
Angular velocity
The rate of change of angle for an object moving in a circular path
Aphelion
The furthest point from the sun in an orbit
Arcminute
A minute of arc 1degrees = 60 arcminutes
Arcsecond
A second of arc 1 arcminute = 60 arcseconds
Astronomical unit
The mean distance from the earth to the sun = 1.5x10^11m
Avogadro constant
The number of atoms in 0.012kg (12g) of carbon-12 = Na
Big bang
The theory that at a moment in the bast all the matter in the universe was contained in a single point the beginning of space and time that expanded rapidly outwards
Black body
An idealised object that absorbs all the em radiation incident on it and when in thermal equilibrium emits a characteristic distribution of wavelengths at a specific temperature
Black hole
The remnant core of a massive star after it has gone supernova and the core has collapsed so far that in order to escape it an object would need an escape velocity greater than the speed of light therefore nothing can escape
Blue shift
The shortening of observed wavelength that occurs when a wave source is moving towards the observer - if a galaxy is moving towards the earth, the absorption lines in its spectrum, will be blue-shifted moved towards the blue end of the spectrum
Boltzmann constant
The molar gas constant R divided by the avogadro constant Na, a constant that relates the mean kinetic merge of the atoms or molecules in a gas to the gas temperature - k
Boyle’s law
The pressure of an ideal gas is inversely proportional to its volume - provided that the mass of gas and the temperature do not vary
Brownian motion
The continuous random motion of small particles suspended in a fluid, visible under a mircoscope
Celsius scale
A temperature scale with 100 degrees between the freezing point and the boiling point of pure water
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 a body moving with a constant speed in a circular path
Chandrasekhar limit
The mass of a star’s core beneath which the electron degeneracy pressure us sufficient to prevent gravitational collapse
Comet
A small irregular body made of ice, dust and small pieces of rock in an orbit around the sun
Conical pendulum
A simple pendulum that instead of swinging back and forth rotates in a horizontal circle at constant speed
Continuous spectrum
A spectrum in which all visible frequencies or wavelengths are present
Cosmological principle
The assumption that, when viewed on a large enough scale, the universe is homogenous and isotopic and 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
Dark energy
A hypothetical form of energy that fills all of space and would explain the accelerating expansion of the universe
Dark matter
A hypothetical form of matter spread throughout the galaxy that neither emits nor absorbs light - it could explain the differences between the predicted and observed velocities of stars in galaxies
Doppler effect
The change in frequency and wavelength of waves received from an object moving relative to an observer compared with what would be observed without relative motion
Driving frequency
The frequency with which the periodic driver force is applied to a system in forced oscillation
Eccentricity
A measure of elongation of an ellipse
Ellipse
An elongated circle with two foci
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 amount of energy that an electron within an atoms is permitted to process
Equation of state of an ideal gas
PV=nRT where n is the number of moles of gas
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 or electrons that have absorbed energy and been boosted into 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 and the further away the points are apart the faster their relative motion away from each other
Forced oscillation
An oscillation in which a periodic driver force is applied to an oscillator
Free oscillation
The motion of a mechanical system displaced from its equilibrium position and then allowed to oscillate without an external forces
Frequency
The number of complete oscillations per unit time
Galaxy
A collection of stars and interstellar dust and gas bound together by their mutual gravitational force
Gas laws
The laws governing the behaviour of ideal gases
Gas pressure
In stars the pressure of the nuclei in the star’s core pushing outwards and counteracting the gravitational force pulling the matter in the star inwards
Geostationary satellite
A satellite that remains in the same position relative to a spot on the earths surface, by orbiting in the direction of the earth’s rotation over the equator with a period of 24 hours
Grating equation
An equation that can be used to determine accurately the wavelength of monochromatic light sent through a diffraction grating dsin θ = n λ
Grating spacing
The separation between adjacent lines or slits in a diffraction grating
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 of the object increases
Gravitational field strength
The gravitational force exerted 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 a point in the gravitational field- Jkg^-1
Ground state
The energy level with the most negative value possible for an electron within an atom - the most stable energy state of an electron
Heavy damping
Damping that occurs when the damping forces are large and the period of the oscillations increase slightly with the rapid decrease in amplitude
Hertzsprung-russel diagram
A graph showing the relationship between the luminosity of star in our galaxy and their average surface temperature
Homogenous
Uniform in terms of the distribution of matter across the universe when viewed on a sufficiently large scale
Hubble constant
The gradient of best-fit line for a plot of recessional speed against distance from earth of other galaxies
Hubbles law
The recessional speed of a galaxy is almost directly proportional to its distance from the Earth
Ideal gas
A model of a gas including assumptions that simplify the behaviour of real gases
Inflation
A phase of astonishing acceleration of the expansion of the universe thought to have occurred 10^-35s after the big bang
Internal energy
The sum of the randomly distributed kinetic and potential energies of the atoms, ions and molecules within the 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 same in all directions
Kelvin
SI base unit of the absolute temperature scale
Keplers first law
The orbit of a planet is an ellipse with the sun at one of the two foci
Keplers second law
A line segment connecting a planet to the sun sweeps out equal areas during equal intervals of time
Keplers third law
The square of the orbital period T of a planet is directly proportional to the cube of its average distance r from the sun
Kinetic model/Kinetic theory of matter
A model that describes all substances as made of atoms , ions or molecules, arranged differently depending on the phase of the substance
Light damping
Damping that occurs when the damping forces are small and the period of the oscillations is almost unchanged
Light-year
The distance travelled by light in a vacuum in a time of one year
Luminosity
The total radiant power output of a star - unit W
Main sequence
The main period in a stars life, during which it is stable
Maxwell-Boltzmann distribution
The distribution of the speeds is particles in a gas
Mean square speed
The mean of the squared velocities of all the particles in a gas
Microwave background radiation
The microwave signal of uniform intensity detected from all directions of the sky, which fits the profile for a black body at a temperature of 2.7K
Molar gas constant
The constant in the equation of state of an ideal as - R
Molar mass
The mass of one mole of a substance
Mole
The amount of substance that contains as many elementary entities as there are atoms in 12g of carbon-12
Natural frequency
The frequency of a free oscillation
Nebula
A cloud of dust and gas often many hundreds of times larger than our solar system
Neuton star
The remnant core of a massive star after the star has gone supernova (if the mass of the core is greater than Chandrasekhar limit) the core has collapsed under gravity to an extremely high density as it is almost entirely made up of neutrons
Newtons law of gravitation
The force between two point masses is directly proportional to the product of the masses and inversely proportional to the square of the separation between them
Oscillating motion
Repetitive motion of an object around its equilibrium position
Parallax angle
The angle of the apparent shift in the position of a relatively close star against the backdrop of much more distant stars as the earth makes a quarter an orbit around the sun
Parsec
The distance at which a radius of one AU subtends an angle of one arcsecond
Perihelion
The closest point to the sun in an orbit
Period
The time taken to complete one oscillation
Phase
A phase of matter is its state (sold, liquid or gas)
Phase difference
The difference in displacement between two oscillating objects or the displacement of an oscillating object at different times
Planet
An object in orbit around a star with a mass large enough for its own gravity to give it a round shape, that undergoes no fusion reactions and that has cleared its orbit of most other objects
Planetary nebula
The outer layers of a red giant that gave drifted off into space, leaving the hot core behind at the centre as a white dwarf
Planetary satellite
A body in orbit around a planet - it may be natural or artificial
Protostar
A very hot, very dense sphere of condensing dust and gas that is on the way to becoming a star
Radiation pressure
Pressure from the photons in the core of a star which acts outwards to counteract the pressure from the gravitational force pulling the matter in the star inwards
Red giant
An expanding star at the end of its life, with an inert core in which fusion no inter takes place, but in which fusion of lighter elements continues in the shell around the core
Red shift
The lengthening of observed wavelength that occurs when a wave source is moving away from the observer - if a galaxy is moving away from the earth the absorption lines in its spectrum will be red-shifted
Red supergiant
A huge star in the last stages of its life before it explodes in a supernova
Resonance
The increase in amplitude of a forced oscillation when the driving frequency matches the natural frequency of the oscillating system
Root mean square speed
The square root of the mean square speed of all particles in a gas
Satellite
A body orbiting around the planet
Simple harmonic motion
Oscillating motion for which the acceleration of the object is directly proportional to its displacement and is directly towards some fixed point
Solar system
A planetary system consisting of a star and at least one planet in orbit around it
Specific heat capacity
The energy required per unit mass to change the temperature by 1K
Specific latent heat
The energy required to change phase per unit mass while at constant temperature
Specific latent heat of fusion
The energy required to change unit mass of a substance from solid to liquid while at constant temperature
Specific latent heat of vaporisation
The energy required to change unit mass of a substance from liquid to gas while at constant temperature
Spectral line
A line in an emission line spectrum or absorption line spectrum at a specific wavelength
Spectroscopy
A technique in which spectral lines are identified and measured in order to identify elements present within stars
Stefan constant
The constant in Stefan’s law relating the luminosity of a star to its surface area and its absolute surface temperature
Stellar parallax
A technique used to determine the distance to stars that are relatively close to the earth by comparing their apparent positions against distant stars at times 6 months apart
Supernova
The implosion of a red supergiant at the end of its life which leads to subsequent ejection of stellar matter into space leaving an inert remnant core
Thermal equilibrium
A state in which there is no net flow of thermal energy between the objects involved - they must be at they same temperature
Triple point
For a given substance one specific temperature and rescue at which all three phases of the substance can exist in thermodynamic equilibrium
Uniform gravitational field
A gravitational field in which the field lines are parallel and the value for g remains constant
Universe
Everything that exists within space and time e
Warns displacement law
The peak wavelength at which the intensity of radiation from a black body is a maximum is inversely proportional to the absolute temperature of the black body
Absorption line spectrum
A set of specific frequencies of electromagnetic radiation visible as dark lines in an otherwise continuous spectrum on spectroscopy they are absorbed by atoms as their electrons are excited between energy states by absorbing the corresponding amount of energy in the form of photons every element has a characteristic line spectrum
Fiducial marker
A marker for a point used as a fixed basis for measurement or comparison
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 of the object increases
Gravatational field strength
The gravitational force exerted over unit mass at a point within a gravitational field
Gravatational potential
The work done per unit mass to bring an object from infinity to a point in the gravitational field
Negative temperature coefficient
A relationship in which a variable decreases as temperature increases - resistance of ntc thermistors
Neutron star
The remnant core of a massive star after the star has gone supernova and the core has collapsed under gravity to an extremely high density as it is made up of neutrons
Principle of conservation of momentum
Total momentum of a system remains the same before and after a collision
White dwarf
A very dense star formed from the core of a red giant in which no fusion occurs
Wien’s displacement law
The peak wavelength at which the intensity of radiation from a black body is a maximum is inversely proportional to the absolute temperature T of the black body
Young’s modulus
The ratio of tensile stress to tensile strain when these quantities are directly proportional to each other
