## Definitions

**The rule of thumb is to use the worded equation when applicable**

**Highlighted definitions are likely to be asked**

## Mechanics

## Motion

**Acceleration**- The rate of change of velocity

**Area**- The size of a part of a materials surface

**Average Speed**- Measure of the total distance travelled in a unit time

**Displacement**- The distance travelled in a particular direction

**Distance**- Difference between to points in different positionsInstantaneous Speed - Speed at a certain instance

**Kelvin**- Measure of Temperature

**Scalar**- A quantity with only magnitude

**Speed**- The distance travelled per unit time

**Vector**- A quantity with magnitude and direction

**Velocity**- The displacement in a unit time

**Weight**- Gravitational force of an object

## Force in Action

**Braking Distance**- The distance a vehicle travels while decelerating to a stop

**Centre of Gravity/Mass**- The point at which the entire weight of an object is said to act

**Couple**- Two forces that are equal and opposite to each other but not in the same straight line - acting in the same rotational direction

**Crumple Zone**- An area of a vehicle designed to increase the distance over which the vehicle decelerates and so reduces the average force acting

**Density**- Mass per unit volume

**Drag**- Resistive force that acts on an object

**Drag coefficient**- Determines how much drag acts upon the object

**Equilibrium**- Where there is no net force

**Force**- a push or pull

**Free fall**- When an object is accelerating under the force of gravity

**GPS**- A system using trilateration of three satellites giving an exact location

**Gravitational Force**- Acceleration due to gravity (on Earth = 9.81)

**Moment of a force**- The turning effect due to a force multiplied by it's perpendicular distance from a given point

**Newton**- Unit of Force

**Perpendicular**- right angled to

**Pressure**- Force per unit area

**Principle of Moments**- For a body in rotational equilibrium the sum of the clockwise moments equal the sum of the anti-clockwise moments

**Stopping Distance**- The sum of the thinking and braking distance - total distance for a vehicle to stop from point of visual contact with a need to stop

**Thinking Distance**- The distance it takes before the brakes are applied after noticing a need to stop

**Thrust**- Force due to an engine

**Torque**- Turning effect due to a couple

**Upthrust**- A force acting against an objects direction of travel

## Work and Energy

**Brittle**- A material that distorts very little

**Compressive Force**- Two or more forces that has the effect of reducing the volume of an object

**Conservation of Energy**- Energy cannot be created or destroyed only transformed or conserved

**Ductile**- Materials that have a large plastic region

**Efficiency**- The percentage of useful energy output

**Elastic Deformation**- The object will return to its original shape

**Elastic Limit**- The point where elastic deformation becomes plastic deformation

**Elastic Potential Energy**- The energy stored in a stretched or compressed object

**Energy**- The ability to do work

**Extension**- The change in length of an object subject to tension

**Force/Spring Constant**- The constant of proportionality in Hooke's Law

**Hooke's Law**- The extension of an elastic body is proportional to the force that causes it

**Intensity**- The energy incident per square metre of a surface per second

**Joule**- Unit of energy - work done when a force of 1 N moves its point of application 1m in the direction of force

**Plastic Deformation**- The object will not return to its original shape

**Polymeric**- Material which sustains large stress loads

**Power**- The rate of doing work

**Spring Constant**- Force per unit extension

**Strain**- The extension per unit length

**Stress**- The force per unit cross-sectional area

**Tensile Force**- Two or more opposite forces acting on an object extending it

**Tensile Stress**- Tensile force per unit cross sectional area

**Ultimate Tensile Strength/Stress**- The maximum force/stress that can be applied to an object before it breaks

**Young's Modulus**- The ratio of stress and strain

## Electrons, Waves and Photons

## Electrical Current

**Ampere**- Measure of current

**Charge**- Amount of current over a unit time

**Conventional Current**- The assumption current flow is + to -

**Coulomb**- Measure of Charge

**Current**- Flow of charge in a unit time

**Drift Velocity**- The average velocity of an electron as it travels through a wire due to pd

**Electrolyte**- A fluid that contains ions that are free to move

**Electron**- Negatively charged sub-atomic atom

**Electron Flow**- Current moving from - to +

**Kirchhoff's First Law**- The sum of the currents entering a junction are equal to the sum of the currents exiting a junction - conservation of charge

## Resistance

**Conductor**- A material with a high conduction electron number density

**Insulator**- Opposite of conductor

**Ohm**- Unit of resistance

**Ohm's Law**- The electric current through a conductor is proportional to the potential difference across it provided it is under standard conditions

**Resistance**- Regulation of current through a material

**Resistivity**- The intrinsic properties of a metal (best defined with equation)

**Semiconductor**- A material that electrons move when put in a circuit leaving gaps for electrons to replace

## DC Circuits

**Ammeter**- A device connected in series to measure current

**Components**- Parts of electrical circuit

**Electromotive Force**- Electrical Energy transferred per unit charge when chemical is turned into electrical energy

**Electronvolt**- Energy change of one electron when it moves through a pd of 1V

**Fuse**- Component designed to melt when overloaded with current

**Internal Resistance**- The resistance of a battery or cell

**Kilowatt hour**- Unit of energy to monitor energy usage in a household

**Kirchhoff's Second Law**- The sum of the emfs is equal to the sum of the pds through a closed group

**Light Dependent Resistor**- Component that increases its resistance when light intensity decreases

**Light Emitting Diode**- A component that allows current traveling in one direction through

**Parallel Circuit**- Where there are components on separate loops

**Potential Difference**- Electrical Energy transferred per unit charge when electrical energy is converted into other energy

**Potential Divider**- A circuit designed to divide up the pds in proportion to the resistance of the components

**Power**- The rate of doing work

**Series Circuit**- Where all the components are on the same loop

**Volt**- Unit of pd or emf

**Voltmeter**- Device connected parallel to measure the pd across a loop

**Watt**- Unit of Power

## Waves

**Amplitude**- Maximum displacement of a wave from rest position

**Antinode**- Point of maximum amplitude caused by constructive interference

**Coherence**- Two waves constatly in phase

**Diffraction**- Spreading of a wave round an obstacle

**Electromagnetic Wave**- A self-propagating transverse wave that doesn't require a medium to travel through

**Frequency**- Number of oscillations per unit time

**Fundamental Frequency**- The lowest frequency in a harmonic series where a stationary wave forms

**Gamma Rays**- Electromagnetic wave with wavelength between 10^(-16 to -9)

**Harmonics**- Whole number multiples of the fundamental frequency of a stationary wave

**Infrared**- A form of electromagnetic wave with wavelength between 10^(-6 to -3)

**Interference**- The addition of two or more waves resulting in a new wave pattern

**Longitudinal Wave**- A wave where oscillations are parallel to the direction of wave propagation

**Malus' Law**- The change in intensity of a transverse wave passing through a Polaroid Analyser

**Microwaves**- Electromagnetic wave with wavelength 10^(-4 to -1)

**Monochromatic Light**- Light waves with a single frequency or wavelength

**Node**- A point where there is always zero amplitude caused by destructive interference

**Period**- Time taken to complete one oscillation

**Phase Difference**- The difference between two waves traveling parallel to each other

**Plane Polarised Wave**- A transverse wave operating in one plane

**Polarisation**- Turning of an unpolarised wave into a polarised wave

**Progressive Wave**- A wave that travels from one point to another

**Propagation**- The way a wave travels

**Radian**- A measure of angle

**Radiowave**- Electromagnetic wave with wavelength 10^(-1 to 4)

**Reflection**- Rebound of waves off a surface

**Refraction**- Change in direction of waves into a different medium

**Standing/Stationary Wave**- A wave formed by the interference of two waves traveling in opposite directions

**Superposition**- When two or more waves of the same type exist in the same place the resultant wave will be found by adding the displacements of the individual waves

**Transverse Wave**- A wave where the oscillations are perpendicular to the direction of wave propagation

**Ultraviolet**- Electromagnetic wave with wavelengths 10^(-9 to -8)

**Wave**- A series of vibrations that transfer from one point to another

**Wavelength**- Smallest distance between on point to it nearest adjacent identical point on the next wave

**X-ray**- Electromagnetic wave with wavelength 10^(-12 to -7)

**Young's double Slit**- Experiment to show wave nature of light via superposition and interference

## Quantum Physics

**Absorption Spectrum**- A spectrum of dark lines across the pattern of spectral colours produced when light passes through a gas

**de Broglie Equation**- Ratio of Planck's Constant to momentum

**Electron Diffraction**- The process of diffracting an electron through a gap

**Emission Spectrum**- A pattern of colours of light, each colour relating to a specific wavelength

**Energy Levels**- One of the specific energies of electron can have when in an atom

**Line Spectrum**- A spectrum of certain spectral colours produced when passed through a material

**Photocell**- A component that reduces its resistance when light shines on it due to the photoelectric effect

**Photoelectric effect**- The emission of electrons from the surface of a material when UV light is incident on the surface

**Photon**- A quantum packet of energy or light

**Spectral Line**- A line of a certain colour assigned to a discrete wavelength

**Spectrum**- A collection of waves with a range of frequencies

**Threshold Frequency**- The lowest frequency of electromagnetic radiation that will result in the emission of photoelectrons from a specific metal

**Wave-particle duality**- The theory that states all objects can exhibit both wave and particle properties

**Work function Energy**- The minimum energy required to release an electron from a material