Our Dynamic Universe
Distance
Scalar quantity - How far the object actually moved
Displacement
Vector quantity - How far is the End point from the Start
Speed
Scalar quantity - Distance / Time
Velocity
Vector quantity - Displacement / Time
Angular Velocity
The Rate of change of Angular displacement
Tangential Velocity
The Linear Velocity of an object traveling in a circle. It is the velocity with which the object would move if the Centripetal Force was removed.
Acceleration
"The Rate of Change of Velocity" or the "Change in Velocity per second"
Angular Acceleration
The Rate of Change of Angular Velocity.
Radial Acceleration
The Acceleration towards the Center of a Circular motion, caused by a Centripetal Force.
Centripetal Force
Force inwards towards the Centre of a Circular motion.
Newton's First Law
An object will remain at rest or travel with a constant Velocity unless acted on by an unbalanced Force
Newton's Second Law
The acceleration of an object is directly proportional to the unbalanced force and inversely proportional to its mass
or
F = ma
Newton's Third Law
If A exerts a force on B, then B exerts an equal but opposite force on A
Torque
The Turning Effect of a Force at a set distance from a pivot point, measured in Nm.
Law of Conservation of Energy
Energy can not be created or destroyed, only changed from one form into another
Law of Conservation of Momentum
In a collision where no external forces act, the total momentum before = the total momentum after
Angular Momentum
The product of the angular velocity of a rotating object and its moment of Inertia, measured in kgm2s-1.
Law of Conservation of Angular Momentum
In a collision where no external Torques act, the total angular momentum before = total angular momentum after.
Elastic Collision
Both Momentum and Kinetic energy are conserved
Inelastic Collision
Momentum is conserved, Kinetic Energy is NOT conserved
Low Earth Orbit
Orbital Period ~ 90 Minutes
Mainly Used for Earth Observation Satellites
Geostationary Orbit
Orbital Period = 1 day
For an Observer on the Earth, a Geostationary Satellite will appear stationary in the sky.
Gravitational Field Strength
The Force exerted upon a mass of 1 kg at a certain point within a Gravitational Field
Gravitational Potential
The Work Done by an external Force to bring a Unit Mass from infinity to that point.
Gravitational Lensing
The bending of Light around a massive object, caused by the light following a straight path through Curved Space-Time
Escape Velocity
The Minimum velocity required for an object to escape ( to infinity ) the Gravitational field of another object.
Schwarzschild Radius
The Distance from the centre of a Black hole at which the Escape Velocity is equal to the Speed of Light. Also known as the Event Horizon
Singularity
A 1-dimensional point of infinite density at the centre of a Black Hole
Time Dilation
( Special Rel )
The apparent increase in the length of 1 Second, caused by relative motion greater than 0.1 C. The consequence of this is that Time appears to run slower at relativistic speeds.
Time Dilation
( General Rel )
The apparent increase in the length of 1 second, caused by the proximity of an object with a large gravitational field strength.
Length Contraction
The apparent decrease in the length of 1 meter, caused by relative motion greater than 0.1 C. The Consequence of this is that objects appear shorter ( in the direction of travel) at relativistic speeds
Worldline
The Line on a Space-Time diagram showing an object's position within Space-Time.
Protostar
Cloud of Dust and Gas collapsing under Gravity, increasing in Temperature and Pressure ( No Fusion ) .
Main-Sequence Star
Star held in Gravitational Equilibrium, Inwards Gravitational Force balanced by the Outwards Thermal Pressure due to Hydrogen Fusion.
Post Main-Sequence Star
Hydrogen Fusion ends, final fate of the Star dependent on its original Mass.
Black Body Object
An object which perfectly absorbs and emits all frequencies of Electromagnetic radiation.
Luminosity
The Total Power a Star emits across all frequencies
Doppler Effect
Apparent change in the frequency of a Wave due to relative motion
Red Shift
Source Moving Away from Observer, Wavelength appears longer
Blue Shift
Source Moving Towards the Observer, Wavelength appears shorter
Cosmic Microwave Background
The observed background radiation that is present in every direction in the Universe, it provides strong evidence of the Big Bang
Dark Energy
Proposed type of Energy, used to account for the increasing rate of expansion of the Universe.
Dark Matter
Proposed type of Matter, used to account for "missing mass" within the Universe, it cannot be detected by conventional telescopes
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Electricity
Potential Difference ( V )
Work done in transferring one coulomb of charge from one point to another
Current
Rate of Flow of Charge, measured in Amperes
Current
( Electron Flow )
Current Direction used in Scotland, shows the flow of Negative Charge Carriers moving from Negative to Positive
Current
( Conventional )
Current Direction used in rest of World + Engineering in Scotland, shows the flow of Charge Carriers from Positive to Negative.
EMF
The Energy given to each Coulomb of Charge passing through a Cell.
Internal Resistance
The resistance of the Cell itself. A Cell can be modelled as a source of EMF in series with an internal Resistor
Lost Volts
Energy used (by the internal resistance of a battery) by each coulomb of charge passing through the Cell
Terminal Potential Difference
The Voltage of a Cell or Battery as Measured across its terminals
Direct Current
Current ( and Voltage ) are in one direction only. An example of a DC supply is a Battery
Alternating Current
Current ( and Voltage ) continuously change direction. An example of an AC supply is Mains Electricity
Peak Voltage or Current
The highest value reached by an Alternating Voltage or Current
RMS Voltage or Current
The Average value of an Alternating Voltage or Current, causes heating equivalent to the DC Voltage or Current
Electric Field Strength
Force applied to unit charge (1 coulomb) in an electric field
Coulomb's Law
The Electrostatic Force between two point charges is proportional to the product of the two Charges, and inversely proportional to the square of the distance between them.
Electric Potential
The Work Done to move a Unit Positive Charge from Infinity to a point within an Electric Field.
Capacitance
( F )
The Number of Coulombs of charge stored per Volt
Time Constant
The Time Taken for a Capacitor to Charge to 63% of Full Charge, or Discharge to 37% of Full Charge. Can be found by the product of the Capacitance and the Resistance within the Circuit.
Capacitive Reactance
The Opposition to Current Flow in a circuit due to a Capacitor, measured in Ohms.
Magnetic Domain
A Region within a Ferromagnetic material where all atoms are aligned with their Magnetic Fields parallel to each other.
Induced EMF
The EMF generated in a conductor by a changing external Magnetic Field. The Induced EMF always acts to oppose the change which caused it, and therefore is also known as the Back EMF.
Electromagnetic Induction
The magnitude of the EMF produced is proportional to the rate of change of Magnetic Flux through the circuit.
Self Inductance
The generation of a Back EMF within a Coil due to the current flowing within it.
Electron-Volt
Equal to 1.6 x10-19 J. Defined as the Work Done to move a single Electron through a Potential Difference of 1 Volt.
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Particles and Waves
Baryon
A Particle made of Three Quarks
Meson
A Particle made of Two Quarks ( Quark - Anti Quark Pair )
Lepton
A Fundamental Particle of Matter
Boson
A Force Mediating Particle
Anti-Matter
Every particle has an anti-particle. These are identical in every way, but carry the opposite charge. If they meet, they annihilate each other releasing Energy.
Atomic Number
The Number of Protons within the Nucleus of an Atom.
Mass Number
The Number of Nuclear Particles ( Protons + Neutrons ) within the Nucleus of an Atom.
Alpha Decay
Radioactive Emission of an Alpha Particle ( consisting of a Helium Nucleus ) from the Nucleus of an Atom.
Alpha Decay decreases the Mass Number by 4 and the Atomic Number by 2.
Beta Decay
Radioactive Emission of a Beta Particle ( consisting of a High Energy Electron ) from the Nucleus of an Atom. Beta Decay does not change the Mass Number, but increases the Atomic Number by 1.
Gamma Decay
Radioactive Emission of a Gamma Ray from the Nucleus of an Atom. Gamma decay does not change either the Mass Number or the Atomic Number.
Nuclear Fission
A Large Atomic Nucleus is Split into two ( or more ) smaller Nuclei, releasing several Neutrons and Energy.
Nuclear Fusion
Two small Nuclei combine under high temperatures and pressures to form a larger Nucleus, releasing Energy.
Simple Harmonic Motion
The motion of an Object oscillating around a fixed equilibrium position. The acceleration of the Object is proportional to its displacement, and is always directed towards the equilibrium point.
Travelling Wave
A Wave in which Energy is transferred from one point to another by vibrations.
Stationary Wave
A Wave in which the points of zero and maximum displacement do not move through the medium.
Node
A point on a Standing wave where there is zero displacement. Occurs due to destructive interference between the incident and reflected wave.
Damping
A decrease in the amplitude of oscillations due to the loss of energy from the oscillating system, for example the loss of energy due to work against friction.
Wavelength
The distance between any two repeating points within a Wave, measured in Meters.
Amplitude
The vertical distance between the peak ( or trough ) of a wave and the Equilibrium Point.
Period
The Time Taken for One wave to Pass a point, measured in Seconds.
Frequency
The Number of Waves passing a point in One Second, measured in Hertz.
Coherent Wave
Coherent Waves have Same frequency, wavelength and speed and are in phase.
Constructive Interference
When 2 wave crests or 2 wave troughs arrive at the same point at the same time, they are said to be in phase, causing a Maximum. The superposition of these two waves results in a stronger signal.
Destructive Interference
When a wave crest and a wave trough arrive at the same point at the same time, they are said to be out of phase, causing a Minimum. The superposition of these two waves causes the signals to be cancel each other out.
Optical Path Difference
The Optical Path is equal to the product of the Physical Path Difference and the Refractive Index. Used when two rays pass through materials with different Refractive Indices before interfering.
LASER
Light Amplification by Stimulated Emission of Radiation, gives Monochromatic and coherent light
Point Source
A source which emits Electromagnetic Radiation equally in all directions.
Irradiance
The amount of Light Energy incident on every square metre of a surface per second.
Work Function
The minimum energy which must be supplied to by each Photon enable an electron to escape from a metal surface.
Threshold Frequency
The Minimum Frequency of a Photon required to cause an Electron to undergo Photoelectric Emission.
Spontaneous Emission
Light is emitted when electrons in an excited state drop to a lower energy level. Emitting photons in any direction, randomly.
Stimulated Emission
An incoming photon causes an electron to jump down to a lower energy level and emit a photon. The photons are in phase and moving parallel to each other in the same direction.
Stimulated Absorption
Incoming photons are absorbed by electrons in a lower energy level causing them to jump to a higher energy level.
Unpolarised Light
Light in which the Electric Field oscillations occur in random Planes.
Optical Activity
The effect of some materials of rotating the Plane of Polarisation of a Beam of Light passing through it.
Polarised Light
Light in which all Electric Field oscillations are in one Plane.
Saccharimetry
Technique that uses the Optical Activity of a Sugar solution to measure its concentration.
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Miscellaneous
Mains supply frequency - 50Hz
Mains supply voltage - 230V
Evidence for particle theory - Photoelectric effect
Evidence for wave theory/ test for wave - Interference Patterns
Dispersion using a prism - Red deviates least, Violet deviates most
Interference diffraction grating - Red deviates most, Violet deviates least