# Physics 2

Physics 2

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## ENERGY

Energy is neither created or destoryed, it is converted from one form to another.

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## EFFICIENCY

Efficiency = Useful energy output / total energy input

x 100

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## CONDUCTION

Is the transfer of thermal energy through a substance without the substance moving

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## CONVECTION

Is the transfer of heat energy through fluids by the upward movement of warmer, less dense region in the fluid being pushed away by the colder and therefore denser fluid.

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Is the transfer of heat energy in the form of infrared waves. The only method of hear transfer through a vacuum.

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## WORK DONE (jOULES)

Work DOne (joules) = Force (Newtons) x DIstance (metres)

Energy transferred = Work Done

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## Gravitational Potential Energy

GPE (Joules) = mass (kg) x gravitational field strength x height (m)

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## KINETIC ENERGY

Kinetic Energy = 1/2 x mass x speed squared

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## POWER

Is the rate of transfer of energy or the rate of doing work

Power = Work Done / TIme

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## DENSITY and PRESSURE

Density (kg/m3) = mass / volume

Pressure (Pascals)= Force / Area

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## PRESSURE

In solds exert downward force

In liquid at any point act in all directions and increases with depth

Pressure DIfference = Height (m) x Density (kg/m3) x g

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## BROWNIAN MOTION

Particles in matter ar extremely small and in fluids they are in continous state of rapid random motion.

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## BOYLE'S LAW

For a fixed amount of gas at a constant temperature pressure is inversely proportionate to the volume

Pressure 1 x Volume 1 = Pressure 2 x Volume 2

P1/P2 = V2/ V1

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## TEMPERATURE

0 degress Kelvin = -273 degrees celcius

For a fixed amount of gas at constant volume

P1/T1 = P2/T2

Therefore pressure is proportionate to kelvin Temperature

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## WAVES

Transfer energy from one place to another without transfering matter

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## WAVELENGTH

The distance between corresponding points in the wave

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## AMPLITUDE

The maximum displacement of a part of the medium from its rest position

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## PERIOD

The time for one complete cycle of the wave form

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## FREQUENCY

The number of cycles of waveform per second

Frequency = 1/period

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## WAVE EQUATION

Wave speed = Frequency x wavelength

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## LAW OF REFLECTION

ANGLE OF INCIDENCE = ANGLE OF REFLECTION

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n = sini/ sin r

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## ELECTROMAGNETIC SPECTRUM

Miles                                        Micro Waves

In                                               Infrared

Very                                          Visible Light

Uncomforatble                        Ultraviolet

eXtreme                                     X-rays

Games                                     Gamma rays

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## ISOTOPES

Are substances of the same element with the same number of protons but different number of neutrons.

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A radioactive substance has an unstable nuclei and will emit radiation to make the nucleus more stable

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Is a random process when the nucleus emits a radioactive particle under-goes a change in structure except gamma radiation as has no mass or charge

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## HALF LIFE

Half life of radioactive isostope is the time taken for half the original number of unstable nuclei to decay

The time taken for the activity of a radioactive substance to fall to half its original value.

Becquerels (Bq)

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## FISSILE

Can be split into lighter element quite easily

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## ELECTROMAGNETS

A current in a coil of wire produces a magnetic field

1) Increasing current

2) Increasing number of turns in coil

3) By winding coil around a magnetic material

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## ELECTROMAGNETIC INDUCTION

When a conductor is in a changing magnetic field a voltage will be induced in the conductor or when it moves through a magnetic field. If the conductor is part of a closed electric circuit then the induced voltage will cause a current to flow.

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## TRANSFORMERS

Function = change size of an alternating voltage. Done by having two separate coils with different numbers of turns.

Input Voltage/ Output voltage = Primary turns / Secondary Turns

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