Our Dynamic Universe 


Scalar quantity - How far the object actually moved 


Vector quantity - How far is the End point from the Start 


Scalar quantity - Distance / Time 


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. 


"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


F  =  ma 

 Newton's Third Law

If A exerts a force on B, then B exerts an equal but opposite force on A 


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


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


The Line on a Space-Time diagram showing an object's position within Space-Time. 


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. 


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 



 Potential Difference ( V ) 

Work done in transferring one coulomb of charge from one point to another 


Rate of Flow of Charge, measured in Amperes 


( Electron Flow )

Current Direction used in Scotland, shows the flow of Negative Charge Carriers moving from Negative to Positive   


( Conventional )

Current Direction used in rest of World + Engineering in Scotland, shows the flow of Charge Carriers from Positive to Negative.   


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.


( 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. 


Equal to 1.6 x10-19 J. Defined as the Work Done to move a single Electron through a Potential Difference of 1 Volt. 


Particles and Waves 


A Particle made of Three Quarks  


A Particle made of Two Quarks ( Quark - Anti Quark Pair )


A Fundamental Particle of Matter 


A Force Mediating Particle 


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.


A point on a Standing wave where there is zero displacement. Occurs due to destructive interference between the incident and reflected wave.  


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.



The distance between any two repeating points within a Wave, measured in Meters.  


The vertical distance between the peak ( or trough ) of a wave and the Equilibrium Point.  


The Time Taken for One wave to Pass a point, measured in Seconds. 


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. 


Light Amplification by Stimulated Emission of Radiation, gives Monochromatic and coherent light 

Point Source 

A source which emits Electromagnetic Radiation equally in all directions.


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.


Technique that uses the Optical Activity of a Sugar solution to measure its concentration.



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