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Displacement
Position of an object relative to its starting position.
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Velocity
Rate of change of displacement.
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Speed
Rate of change of distance.
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Acceleration
Rate of change of velocity.
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Newton's First Law
An object continues in uniform motion in a straight line/ at rest unless a resultant force acts.
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Newton's Second Law
The acceleration of an object is proportional to and in the same direction as its resultant force.
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Newton's Third Law
When 2 objects react, the exert equal and opposite forces on each other.
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Linear Momentum
The product of mass and velocity.
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Impulse
Change in momentum.
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Law of conservation of momentum
Momentum of object in system stays the same in a closed system.
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Work
Force X distance moved in direction of force.
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Kinetic Energy
The energy an object has due to it's motion
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Change in GPE
The energy an object has due to its position above the Earth.
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Elastic Collision
KE is conserved and objects bounce off with the same speed it did before in opposite directions.
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Inelastic Collision
Maximum loss of KE, objects stick together & momentum is still conserved.
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Explosion
Objects move away from each other, internal energy becomes KE.
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Efficiency
Ratio of work out: energy put in.
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Mole
Amount of substance that has the same number of molecules as the number of of molecules as the number of atoms in 12g of C-12.
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Molar Mass
Mass of 1 mole of the substance.
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Avogadro's Constant
Number of molecules in 1 mole = 6.022 × 10²³
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Specific Heat Capacity
The energy needed to increase the temperature of of 1 kilo of an object by 1K.
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Thermal Capacity
The energy needed to increase the temperature of an object by 1K.
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Specific Latent Heat
Amount of heat needed to change the state of 1 kilo of a substance WITHOUT a change in temperature.
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Pressure
Force per unit area.
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Displacement (SHM)
Distance away a particle is from its equilibrium position.
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Amplitude (SHM)
Maximum displacement of a particle from its equilibrium position.
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Frequency (SHM)
Number of oscillations produced per second.
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Period (SHM)
Time taken for a complete oscillation.
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Phase Difference (SHM)
The fraction of an oscillation that one wave moves behind another.
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Simple Harmonic Motion
Motion where the acceleration of an object is proportional to & in the opposite direction to displacement. a = -ω2x
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Damping
Process where the energy of an oscillating system decreases with amplitude by a dissipative force acting in the opposite direction.
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Natural frequency
The frequency that a system naturally oscillates at.
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Forced oscillation
An oscillation that occurs & stays , Where an object is forced to oscillate by an external force.
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Resonance
When the frequency of a driving force matches the natural frequency of oscillation.
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Transverse wave
Oscillations are at 90° to direction of energy transfer/ wave motion.
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Longitudinal wave
Oscillations are parallel to direction of energy transfer/ wave motion.
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Crest
Point on a wave with maximum positive displacement.
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Trough
Point on a wave with maximum negative displacement.
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Compression
Region (on a wave) where particles are closer together than they would be in their equilibrium state.
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Rarefaction
Region (on a wave) where particles are further apart than they would be in their equilibrium state.
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Wavelength
The shortest distance between 2 points on a wave that are in phase.
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Wave speed
The speed at which wave fronts pass a stationary observer.
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Intensity
The power per unit area received by an observer from a wave.
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Principle of superposition
When 2 or more waves of the same type meet, the total displacement at a point on a wave is the displacements of the individual waves added at that point.
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Constructive/destructive interference
Phase difference is 0/ out of phase& path difference is a whole 'n' of wavelength/ a fraction of it.
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Electric potential difference
Work done per unit charge in moving a positive charge from one point in the (electric) field to another.
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Electronvolt
The amount of energy an electron gains by moving through a potential difference of 1 volt.
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Electric current
The rate of flow of electrical charge.
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Resistance
The ratio of voltage across the material to the current flowing through it.
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Ohm's Law
The current through a wire is proportional to the p.d. across it; as long as the temperature is constant.
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Electromotive force (emf)
The power supplied by the supply per unit current.
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Internal resistance
Resistance of a source (of power).
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Gravitational field strength
The force per unit mass experienced by a small test mass placed in the field.
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Newton's universal law of gravitation
Any point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to their separation².
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Electric field strength
The force per unit charge experienced by a small test charge placed in the field.
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Magnetic field strength
- F=BILsinø
- Direction: 90° to field lines.
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Nuclide
An atom with a particular nucleus configuration.
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Nucleon
A proton or a neutron.
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Isotope
An element with the same number of protons but a different number of neutrons.
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Radioactive half life
The time taken for the total number of nuclei (of a radioactive substance) to halve.
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Unified atomic mass
The mass of ½ of the nucleus of a C-12 isotope.
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Mass defect
The difference in mass between a nucleus and its separate nucleons.
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Binding energy per nucleon
The total binding energy for the nucleus divided by the total number of nucleons
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Binding energy
The energy needed to break up a nucleus into its constituent nucleons.
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Degraded energy
Energy transferred to surroundings that can no longer do useful work.
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Energy density
The mean energy liberated per kg of a fuel.
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Fuel enrichment
A process where you increase percentage of U-235 to make fission more likely.
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Moderator
Slows down fast neutrons to increase the chance of more reactions. (So they don't pass through the nuclei)
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Control rod
This absorbs neutrons to control chain reactions.
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Heat exchanger
This allows the nuclear reactions to occur in a place that is sealed off from the rest of the environment. The thermal energy is transferred to heat water, and the steam that is produced turns the turbines.
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Photovoltaic cell
Light hits semiconductors & electrons are released/ moved; creating an electric field.
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Solar heating panel
Heat goes through glass pane & is absorbed by black pipes with running water in them.
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Albedo
The ratio of reflected: incident radiation.
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Stefan- Boltzmann law
Total power radiated ∝ T⁴ OR P= σAT⁴.
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Emissivity
The ratio of power emitted by a body to the power emitted if it was a black body.
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Surface heat capacity
The energy needed to raise the temperature of a unit area of a planet's surface by 1K.
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Enhanced greenhouse effect
Rising global temperatures due to greenhouse gases being put into the atmosphere because of human activities
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Coefficient of volume expansion
The fractional change in volume per degree change in temperature.
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Gravitational potential
Work done per unit mass in bringing a test mass from infinity to that point in the field.
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Gravitational potential energy
Work done in moving an object from infinity to that point.
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Electric potential
The work done per unit charge in bringing a positive test charge from infinity to that point in the field.
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Electric potential energy
The work done moving a charge from infinity to a point in an electric field.
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Isochoric
Constant volume: no work is done.
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Isobaric
Constant pressure: Work done is area under line.
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Isothermal
Constant temperature: Work done= area under curve.
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Adiabatic
No heat transfer: compression/ expansion. Work is done on/ by gas
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Standing waves
Transfer no energy. They have the same amplitude and are in phase. Happens when a wave & its reflection interfere (or just 2 waves)
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One dimensional standing wave
Happens when a wave reflects back from a boundary along the route it came.
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Doppler Effect
The change in perceived frequency because the source or observer is moving.
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Rayleigh criterion
2 points will be resolvable if the first minimum of the diffraction pattern of one source overlaps the central maximum of the diffraction pattern of the second source.
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Polarized light
Light with waves that vibrate in 1 plane.
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Brewster's angle
Happens when the transmitted ray is 90° to the reflected ray. The angle gives us the angle of incidence needed for plane-polarized light.
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Polariser
A device that makes polarized light from an unpolarised beam.
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Analyser
A polariser used to detect polarised light.
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Optically active substance
A substance that rotates the plane of polarisation of light that goes through it.
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Stress analysis
If polarised white light is shone on plastic, you can see the stress points where the coloured lines are.
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Magnetic flux
A measure of the strength of a magnetic field over a given area/ number of field lines.
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Magnetic flux linkage
The product of the magnetic flux and the number of turns in a given coil.
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Faraday's law
The size of an induced emf is proportional to the rate of change of flux linkage.
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Lenz's law
The direction of an induced current is such that it'll oppose the change causing it.
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de Broglie Hypothesis
All particles have a wave like nature.
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Electron in a box model
An electron has possible wavelengths like a standing wave on a string so electrons have discrete energies.
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Schrödinger's model
This gives the probability of where the electron could be (probability regions called orbitals).
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Heisenberg uncertainty principle
- You can only know 1 from each pair:
- -momentum & position
- -energy & time
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Decay constant
Probability of decay of a nucleus per unit time
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Radioactive decay law
The activity of a radioactive sample ∝ Number of radioactive nuclei present.
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Capacitance
Charge per unit p.d. that can be stored on a capacitor.
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Quantum efficiency
The ratio of the number of photoelectrons emitted: the number of photons incident on the pixel.
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Magnification
The ratio of the length of the image on the CCD: the length of the object.
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Stellar cluster
A group of stars that are physically near each other in space.
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Constellation
A pattern of stars as seen from Earth that aren't physically near each other in space.
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Light year
The distance that light travels in 1 year.
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Luminosity
The total power emitted by a star.
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Apparent brightness
The power received per unit area on Earth by a star.
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Cepheid
A slightly unstable star that has a regular variation in brightness and luminosity due to a periodic expansion and contraction in its outer layers.
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Red giant
- -Red
- -Comparatively cool
- -Large
- -Fuse elements other than Hydrogen
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Red Supergiant
- -Red
- -Large Mass
- -Large Surface Area
- -Large Luminosity
- -Low Surface Temperature
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White Dwarfs
- -Very Small/ Low Surface Area
- -Large Surface Temperature
- -White
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Visual Binary
Stars can be distinguished using a telescope
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Spectroscopic Binary
Analysis if its light spectrum shows 2 different classes of stars- the wavelengths show a periodic splitting in frequency.
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Eclipsing binary
Analysis of the brightness of its light spectrum shows periodic dips. This is because on star is in the way of the other.
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Parsec
A unit of distance that is equal to 3.26 light years
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Apparent magnitude
How bright a star appears from Earth.
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Absolute magnitude
The apparent magnitude a star would have if it was 10 parsecs away.
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Critical density
The theoretical density of the universe that would create a flat universe.
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Hubble's Law
The recessional velocity of a galaxy ∝ its distance away from Earth.
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Audible frequencies
2Hz - 20KHz
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(Sound) Intensity
Amount of energy that a sound wave brings to a unit area every second.
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(Sound) Intensity Level
- 10 lg (I / I0);
- where I0 = 1.0 × 10-12 Wm-2.
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Attenuation Coefficient
The probability of a single photon being absorbed in 1 m of the material- use defining equation.
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Half-value thickness
The half-value thickness is that thickness of material which will reduce the intensity of the (transmitted) beam by 50%
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Acoustic Impedance
The product of of the density of a substance and the speed of sound in that substance.
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Exposure
The total ionized charge produced in unit mass of air by a particular radiation. Q=mX.
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Absorbed Dose
The energy absorbed per unit mass of tissue. E=mD.
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Quality Factor
This allows doses of different types of radiation to be compared for their biological effects.
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Dose Equivalent
The amount of energy absorbed
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Physical Half-Life
- The time it takes for the activity of a sample
- to halve.
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Biological Half-Life
The time it takes the body to naturally eject half of an ingested sample of a radioactive isotope.
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