Year 1 Glossary Flashcards
To learn year 1 physics keywords
Acceleration
Change of velocity per unit time
Acceleration of free fall
Acceleration of an object acted only by the force of gravity
Accuracy
a measurement that is obtained, using accurately calibrated instruments correctly, is said to be accurate
Alpha radiation
Particles that each consist of two protons and two neutrons
Amplitude
The maximum displacement of a vibrating particle from equilibrium
Annihilation
When a particle and its antiparticle meet, they annihilate/destroy each other producing photons of energy
Antibaryon
A hadron consisting of three antiquarks
Antimatter
Antiparticles that each have the same rest mass and have equal and opposite charges to their corresponding particles.
Antinode
A fixed point in a stationary wave pattern where the amplitude is maximum
Atomic number
The number of protons in the nucleus of an atom
Baryon
A hadron consisting of three quarks
Base units
The units that define the SI system(e.g. metre, kilogram, second, ampere)
Beta minus radiation
Beta minus particles are fast moving electrons emitted by an unstable neutron-rich nuclei
Beta plus radiation
Best plus particles are fast moving positrons emitted by unstable proton-rich nuclei
Braking distance
the distance travelled by a vehicle in the time taken to stop it
Brittle
A material that snaps without stretching or bending when subjected to stress
Centre of mass
The point of a body through which a single force on the body has no turning effect
Charge carriers
Charged particles that move through a substance when a pd is applied across it
Kirchhoff’s 1st Law
Circuit rules for current
- The current passing through two or more components in series is the same through each component
- At a junction, the total current in = total current out
Kirchhoff’s 2nd Law
Circuit rules for PD
- For two or more components in series, the total pd across all the components is equal to the sim of the pd’s across each component
- The sum of the emf’s round a complete loop in a circuit = the sum of the pd’s round the loop
Coherent
Two sources of waves are coherent if they emit waves with a constant phase difference
Couple
Pair of equal and opposite forces acting on a body but not along the same line
Critical temperature of a superconducting material
the temperature at and below which the resistivity of the material is zero
Cycle
Interval for a vibrating particle from a certain displacement and velocity to the next time the particle has the same displacement and velocity
De Broglie hypothesis
Matter particles have a wave-like nature characterised by the de Broglie wavelength
De Broglie wavelength
the wavelength of a matter particle = h/p, where p is the momentum of the particle
De-excitation
Process in which an atom loses energy by photon emission, as a reslut of an electron inside an atom moving from an outer shell to an inner shell
Density of a substance
Mass per unit volume of the substance
Diffraction
Spreading of waves on passing through a gap or near an edge
Diffraction grating
A plate with many closely rules parallel slits on it
Dispersion
The splitting of a beam of white light by a glass prism into colours
Displacement
Distance in a given direction
Drag force
The force of fluid resistance on an object moving through the fluid
Ductile
A material that stretches easily without breaking
Efficiency
The ratio of useful energy transferred by a machine or device to the energy supplied to it
Effort
The force applied to a machine to make it move
Elastic limit
The point beyond which a wire permanently stretched
Elasticity
Property of a solid that enables it to regain its shape after it has been deformed or distorted
Electrolysis
Process of electrical conduction in a solution or molten compound due to opns moving to the oppositely charged electrode
Electrolyte
A solution or molten compound that conducts electricity
Electromagnetic radiation
An electric and magnetic wavepacket that can travel through free space
Electromotive force
The amount of electrical energy per unit charge produced inside a source of electrical energy
Electron capture
A process in which an inner shell electron of an atom is captured by the nucleus
Electron volt
Amount of energy equal to 1.6*10^-19J defined as the work done when an electron is moved through a pd of 1V.
Endoscope
An optical fibre device used to see inside cavities
Energy
The capacity to do work
Energy levels
The energy of an electron in an electron shell of an atom
Equilibrium
State of an object when at rest or in uniform motion
Error bar
Representation of uncertainty on a graph
Error of measurement
Uncertainty of a measurement
Excitation
The process in which an atom absorbs energy without becoming ionised as a result of an electron inside an atom moving from an inner shell to an outer shell
Feynman diagram
Representation of the interaction between particles or antiparticles or the decay of a particle or antiparticle
Fluorescence
Glow of light from a substance exposed to UV radiation, the atoms de-excite in stages and emit visible photons in the process
Force
Any interaction that can change the velocity of an object
Free-body force diagram
A diagram of an object showing only the forces acting on the object
Frequency
the number of cycles of a wave that pass a point per second
Friction
Force opposing the motion of a surface that moves or tries to move across another surface
Fundamental mode of vibration
A pattern of stationary waves on a string when it vibrates at its fundamental (lowest possible) frequency.
Gamma radiation
High energy photons emitted by unstable nuclei
Gravitational field strength
Force of gravity per unit mass on a small object
Ground state
The lowest energy state of an atom
Hadron
Particles and antiparticels that can interact through the strong interaction
Hooke’s law
The extenstion of a spring is directly proportional to the force applied up to the limit of proportionality
Inertia
Resistance of an object to change of its motion
Interference
Formation of points of cancellation and reinforcement where two coherent waves pass through each other
Internal resistance
Resistance inside a source of electrical energy, the loss of pd per unit current in the source when current passes through it
Ion
A charged atom
Ionisation
The removal of an electron from an atom
Ionisation energy
The amount of energy needed to completely remove a electron from an atom from the ground state
Isotopes
Atoms of an element with different number of neutrons and the same number of protons
Kinetic energy
The energy of an object due to its motion
Laser
A device that produces a parallel coherent beam of monochromatic light
Leptons
Partices that cannot interact through the strong interaction. The interact through the weak interaction, and in the case of electrons and positrons, through the electromagnetic interaction
Light-dependent resistor
A resistor which is designed to have a resistance that changes with light intensity
Limit of proportionality
The limit beyond which when a wire or spring is stretched, its extension is no longer proportional to the force applied
Linear
Two quantites have a linear relationship if the change of one quantity is proportional to the change of the other
Load
The force to be overcome by a machine when it shifts or raises an object
Longitudinal waves
Waves with a direction of vibration parallel to the direction of propagation of the waves
Mass
Measure of the inertia or resistance to change of motion of an object
Matter waves
The wave-like behaviour of particles of matter
Moment
Force*perpendicular distance from the line of action of the force to the point
Momentum
Mass*velocity
Motive force
The force that drives a vehicle
Multipath dispersion
The lengthening of a light pulse as it travels along an optical fibre, due to rays that repeatedly undergo total internal reflection having to travel a longer distance than rays that undergo less total internal reflection
Negative temperature coefficient
The resistance of a semiconductor decreases when its temperature is increased
Newton’s 1st Law
An object remains at rest or in uniform motion unless acted on by a resultant force
Newton’s 2nd Law for constant mass
The rate of change of momentum of an object is proportional to the resultant force on it
Resultant force = mass*acceleration
Newton’s 3rd Law
When two objects interact, they exert equal and opposite forces on one another
Node
Fixed point in a stationary wave pattern where the amplitude is zero
Nucleon
A neutron or proton in the nucleus
Nucleon number
The number of neutrons and protons in a nucleus
Nuclide
A type of nucleus with a particular number of protons and neutrons
Ohm’s Law
The pd across a metallic conductor is proportional to the current provided the physical conditions do not change
Optical fibre
A thin flexible transparent fibre used to carry light pulses from one end to the other
Pair production
When a gamma photon changes into a particle and antiparticle
Pascal
Unit of pressure or stress equal to 1 N/m
Path difference
The difference in distances betweem two coherent sources to an interference fringe
Period of a wave
Time for one complete cycle of a wave to pass a point
Phase difference
The fraction of a cycle between the vibrations of two vibrating particles measured either in radians or degrees
Photoelectricity
Emissionof electrons from a metal surface when the surface is illuminated by light of frequency greater than the threshold frequency
Photon
Packet or ‘quantum’ of electromagnetic waves
Plane- polarised waves
Transverse waves that vibrate in one plane only
Plastic deformation
Deformation of a solid beyond its elastic limit
Positive temperature coefficient
The resistance of a metal increases when its temperature is increased
Potential difference
Work done or energy transfer per unit change between two points when charge moves from one point to the other
Potential divider
Two or more resistors in series connected to a source of pd
Potential energy
The energy of an object due to its position
Power
The rate of transfer of energy= energy transferred /time taken
Precision of a measurement
The degree of exactness of a measurement, usually expressed as the uncertainty of the readings used to obtain a measurement
Precision of an instrument
The smallest non zero reading that can be measured also sometimes referred to as the instrument sensitivity or resolution
Pressure
Force per unit area acting on a ssurface perpendicular to the surface
Principle of conservation of energy
Energy cannot be destroyed or created
Principle of moments
For an object in equilibrium, the sum of the clockwise moments about any point = the sum of the anticlockwise momens about that point
Probable error
Estimate of the uncertainty of a measurement
Progressive waves
Waves which travel through a substance or through space if electromagnetic
Projectile
A projected object in motion acted on only by the force of gravity
Radian
A measure of an angle defined such that 2pi radians = 360
Random error
Error of measurement due to readings that vary randomly with no recognisable patter or trend or bias
Range of a set of readings
The difference between the maximum and the minimum reading
Range of an instrument
The difference between the maximum and the minimum reading that can be obtain using the instrument
Refraction
Change of direction of a wave when it crosses a boundary where its speed changes
Refractive index
Speed of light in free space/ speed of light in the substance
Resistance
PD/current
Resistivity
resistance per unit length * area of cross section
Rest energy
energy due to rest mass, equal to mc^2, where c is the speed of light in free space
Scalar
A physical quantity with magnitude only
Semiconductor
A substance in which the number of charge carriers increases when the temperature is increased
Sensitivity of an instrument
The output reading per unit input quantity
Specific charge
charge/mass value of a charged particle
Spectrometer
Instrument used to measure light wavelengths very accurately
Speed
Change of distance per unit time
Stationary waves
Wave pattern with nodes and antinodes formed when two or more progressive waves of the same frequency and amplitude pass through each other
Stiffness constant
The force per unit extension needed to extend a wire or spring
Stopping distance
Thinking distance + braking distance
Strain
Extension per unit length of a solid when deformed
Stress
Force per unit of cross-sectional area in a solid perpendicular to the cross section
Strong interaction
Interaction between two hadrons
Strong nuclear force
Attractive force between nucleons that holds the nucleons in the nucleus
Superconductor
A material that has zero electrical resistance
Superposition
The effect of two waves adding together when they meet
Systematic error
Error of measurement due to readings that systematically differ from the true reading and follow a pattern or trend or bias
Terminal speed
The maximum speed reached by an object when the drag force is equal and opposite to the force causing the motion of the object
Thermistor
A resistor which is designed to have a resistance that changes with temperature
Thinking distance
The distance travelled by a vehicle in the time it takes the driver to react
Threshold frequency
The minimum frequency of light that can cause photoelectric emission
Torque of a couple
Force*perpendicular distance between the lines of action of the forces
Total internal reflection
A light ray travelling in a substance is totally internally reflection at a boundary with a substance of lower refractive index, if the angle of incidence is greater than the critical angle
Transverse waves
Waves with a direction of vibration perpendicular to the direction of propagation of the waves
Continuous spectrum
Continuous range of colours corresponding to a continuous range of wavelengths
Line emission spectrum
Characteristic coloured vertical lines each corresponding to a certain wavelength
Line absorption spectrum
Dark vertical lines against a continuous range of colours, each line corresponding to a certain wavelength
Ultimate tensile stress
Tensile stress needed to break a solid material
Uncertainty
Half the range of the readings used to obtain the measurement
Useful energy
Energy transferred to where it is wanted and when it is wanted
Uniform circular motion
Motion of an object moving at a constant speed along a circular path
Vector
A physical quantity with magnitude and direction
Velocity
Change of displacement per unit time
Virtual photon
Carrier of the electromagnetic force, a photon exchanged between two charged particles when they interact
W boson
Carrier of the weak nuclear force, W bosons have non zero rest mass and may be positive or negative
Wave particle duality
Matter particles have a wave-like nature as well as a particle-like nature; photons have a particle-like nature as well as a wave-like nature
Wavefront
Lines of constant phase
Wavelength
The least distance between two adjacent vibrating particles with the same displacement and velocity at the same time
Weak interaction
Interaction between two leptons
Weak nuclear force
The force responsible for beta decay
Weight
The force of gravity acting on an object
Work
Energy transferred by means of a force
Work= force * distance moved in the direction of the force
Work function
The minimum amount of energy needed by an electron to escape from a metal surface
Yield point
A point at which the stress in a wire suddenly drops when the wire is subjected to increased strain
Young’s fringes
Parallel bright and dark fringes observed when light from a narrow slit passes through two closely spaced slits
Young’s Modulus
tensile stress/strain
(assuming the limit of proportionality has not been exceeded)
measured in Pa
Angular displacement
The angle an object in circular motion turns through
Angular speed
The rate of change of angular displacement of an object in circular motion
Angular frequency
For an object oscillating at frequency f in simple harmonic motion, its angular frequency = 2pi * f
Centripetal acceleration
The acceleration of an object moving at speed v in uniform circular motion with the acceleration towards the center of the circle
Centripetal force
The resultant force on an object that moves along a circular path
Conservation of momentum
For a system of interacting objects, the total momentum of the objects remains constant provided no external resultant force acts on the system
Critical angle
The angle that must be exceeded by the angle of incidence for total internal reflection to occur
Damped oscillations
Oscillations that reduce in amplitude die to the presence of resistive forces such as friction and drag
Lightly damped system
the amplitude of the oscillations decreases gradually
Heavily damped system
A system that slowly returns to equilibrium without oscillating after being released from its displacement
Critically damped system
The system returns to equilibrium in the least possible time without oscillating
Forced vibrations
Vibrations of a system subjected to an external periodic force
Free electrons
Electrons in a conductor that move about freely inside the metal because they are not attached to a particular atom
Free vibrations
Vibrations where there is no damping and no periodic force acting on the system, so the amplitude of the oscillations is constant
Gold leaf electroscope
A device used to detect electric charge
Impulse
Force*time for which the force acts
Natural frequency
The frequency of free oscillations of an oscillating system
Principle of conservation of momentum
When two or more bodies interact, the total momentum is unchanged, provided no external forces act on the bodies
Principle of conservation of energy
In any change, the total amount of energy after the change is always equal to the total amount of energy before the change
Resonance
The amplitude of vibration of an oscillating system subjected to a periodic force is largest when the periodic force has the same frequency as the resonant frequency on the system.
Resonant frequency
The frequency of an oscillating system in resonance
Simple harmonic motion
Motion of an object if its acceleration is proportional to the displacement of the object from equilibrium and is always directed towards the equilibrium position
Sinusoidal curves
Any curve with the same shape as a sine wave
