# Physics definitions

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- Created by: RealYorkshireman
- Created on: 09-04-15 12:17

Scalar

A quantity with just magnitude

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Vector

A quantity with magnitude and direction

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Displacement

Distance in a particular direction

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Velocity

The rate of change of displacement

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Acceleration

The rate of change of velocity

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Instantaneous speed

The speed at a given time ( can be seen as the gradient on a distance time graph)

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Average speed

Ratio of distance to time

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Newton

The force required to give a mass of 1kg the acceleration of 1ms^-2

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Terminal velocity

The maximum speed of an object as a result of an equal drag to driving force ( usually the force of gravity)

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Center of gravity

The point through which the weight of an object can be considered to act

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Couple

a pair of equal, parallel forces that produce a rotation

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Torque

One of the forces x the perpendicular distance between the forces

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Moment

Force x perpendicular distance between the force and the pivot/given point

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Thinking distance

The distance a vehicle travels from the instance the driver sees the need to apply the brakes and the instance that the brakes are applied

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Braking DIstance

The distance that the vehicle travels between the instance that the brakes are applied to the instance that the vehicle comes to a complete stop

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Stopping Distance

The sum of the thinking distance and the braking distance

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work done

Force multiplied by the distance in which the force is acting

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Joule

The work done when a force of 1N moves its point of application 1m in the direction of the force

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Conservation of Energy

Energy can not be created or destroyed but may be transferred from one form to another

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Power

The rate of doing work

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Watt

1 joule per second`

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Tensile force

Stretching force; two equal and opposite forces are required to put an object under tension

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Compressive force

Squeezing/Squashing ; two equal and opposite forces acting towards the object.

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Extension

Change in length from the original length

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Elastic limit

The point in which an extended or deformed object will no longer return to its original shape

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Stress

Force per unit Cross sectional area

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Strain

Extension per unit length

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Young's modulus

Ratio of stress to strain ( Stress/Strain)

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Ultimate Tensile Strength

That maximum stress an object can endure before fracture

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Elastic deformation

The deformation of an object which will return to its original shape when the force is removed

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Plastic deformation

The deformation of an object that has resulted in the permanent deformation when the force is removed

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Weight

W = mass x acceleration due to gravity (g)

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Electric current

The net flow of charged particles per unit time through a point

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Conventional current

A model used to describe the movement of charged particles in a circuit

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Electron flow

The movement of electrons around a circuit. Negative to positive

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Electric charge

(C), 1 coulomb being the total charge supplied by a current of 1 ampere in a time of 1 second

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elementary charge

The charge on one electron is 1.6x10^-19

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Kirchoff's 1st law

The sum of the current flowing into a junction is equal to the sum of the current flowing out of the junction as charge is conserved

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Mean drift velocity

The average speed of charged particles along the length of a conductor

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Conductor

A material with a high number density of conduction electrons and therefore a low resistance

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Semi conductor

a material with a low number density of conduction electrons and therefore a high resistance

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Insulator

A material with a number density of conduction electrons nearing 0 and therefore a very high resistance

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Electromotive force (emf)

Energy transferred per unit charge when a type of energy is being converted to electrical energy.

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Potential difference (pd)

Energy transferred per unit charge when electrical energy is converted into another form of energy

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Power

Work done per unit time

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Resistance

Potential difference across a component per unit current

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Ohm's law

the current that flows through a component is directly proportional to the potential difference across it providing physical properties such as temperature remain constant

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Kirchoff's 2nd

The sum of the emfs around a loop is equal to the sum of the pds around the same loop - conservation of charge

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Internal resistance

The resistance of an emf source eg; a cell

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Potential divider circuit

A type of circuit containing two components designed to divide the pd in proportion to the resistances of the components

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Progressive waves

move through a material transferring energy from one position to another

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longitudinal waves

motion of the oscillation of particles is parallel to the direction of the propagation

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Transverse waves

Motion of the oscillations of particles is perpendicular to the direction of the propagation

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Amplitude

Maximum displacement from the point of equilibrium

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Wavelength

The smallest distance between waves - peak to peak / trough to trough

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Period

The time taken to complete one full oscillation ( peak to peak)

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frequency

The number of oscillations passing per second ( f=1/T)

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Phase difference

the proportion of a cycle by which the two waves are "out of sync"

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Wave speed

Speed with which energy is transmitted by a wave v=fλ

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Intensity

Rate of energy transfer per unit area (at right angles to wave velocity)

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Reflection

When waves rebound from a barrier resulting in a change of direction

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Refraction

When waves change direction when they travel from one medium to another due to difference in wave speed in each medium

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Diffraction

When a wave spreads out after passing around and obstacle or through a gap

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Electromagnetic waves

A self-propagating transverse wave that doesnt require a medium to travel through

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Polarity

A wave property that distinguishes between transverse and longitudinal waves

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Plane polarised

A transverse wave that only oscillates in one direction

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Principle of Superposition

the ability for a wave to pass through each other and then continue unaffected

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Interference

The superposition of 2 or more coherent waves resulting a new wave/

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Coherence

two waves with a constant phase relationshop over a significant period of time

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Path difference

The proportion of the wavelength that the 2 waves are 'out of sync'

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Constructive interference

When two waves superimpose to create an increased amplitude

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Destructing interference

When two waves superimpose to create a reduced amplitude

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Stationary waves

A wave pattern produced when two progressive waves of the same frequency travelling in opposite directions superimpose, energy is stored rather than transferred from on place to another

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Antinode

Point of maximum amplitude along a stationary wave

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Node

A point that has 0 amplitude along a stationary wave as a result of destructive interference

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Fundamental mode of vibration

The simplest stationary wave that can be set up where the length of the string is have the wavelength

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Fundamental frequency

Lowest frequency in harmonics series where a stationary wave forms

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harmonics

Whole number multiples of the fundamental frequency of a stationary wave

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Photon

A quantum of energy of EM radiation

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ElectronVolt

The energy change of an electron when it moves through a potential difference of 1 volt

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Work function φ

minimum energy required by a single electron to escape the metal surface

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Threshold frequency

The minimum frequency required to release electrons from the surface of a metal

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De Broglie equation

λ=h/mv - an equation expressing wavelength as a ratio of planck's constant and the particles momentum

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## Other cards in this set

### Card 2

#### Front

A quantity with magnitude and direction

#### Back

Vector

### Card 3

#### Front

Distance in a particular direction

#### Back

### Card 4

#### Front

The rate of change of displacement

#### Back

### Card 5

#### Front

The rate of change of velocity

#### Back

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