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Physics notes

Physics

I know this is really late but I thought I'd post this anyway, its notes on a bunch of stuff that didn't come up on the first exam

*Moments

 moment = force x perpendicular distance from pivot

 
total clockwise moment = anticlockwise moment  

 
weight = mass x gravity

 
*Electromagnetic Spectrum

radio waves

micro waves

infra

red

visable light

ultra

violet

X rays

gamma rays

     increasing wavelength

Radio – communications and TV and radio

Microwaves – cooking food, satellite transmission

Infrared – night vision and remote controls

Visible light – for seeing and optical fibre digital communications (OFDC)

Ultraviolet – used to make fluorescent tubes and used to see hidden security marks

X rays – check for broken bones

Gamma – treat cancer and to sterilise medical equipment

 
#Pressure

*Pressure (Pa)   = force  / area

#Density

*Density   =  mass / volume

#Plugs

* blue - neutral
* brown - live, connected to the fuse
* green/yellow - earth

#Electromagnets

~ a coil of wire (solenoid)  with an iron core
- when current flows through wires, creates magnetic field around it

strenght of electromagnet depends on:

1.)  size of current
2.)  number of turns that the coil has
3.)  what the core is made from

iron - magnetically "soft" , ideal for electomagnets
steel - magnetically "hard" ideal for permanent magets

#Transformers
- change voltage, but only for allernating current voltages

Equation

Primary voltage / Secondary voltage =  No. of turn on primary / No. of turns on secondary

#Graphs

Distance /Time

- gradient = speed
- flat sections - stopped
- steeper the graph - faster its going
- downhill - coming back to starting point
- curves - accelerating or deccelerating
- steeping curve - speeding up
- leveling  off curve - slowing down

Velocity / Time
- gradient = accelerating
- flat sections - steady speed
- steeper the graph , greater the acceration or decceleration
- unhill sections - acceleration
- down hill - decceleration
- area under any section - distance
- curve - changing acceleration
 
# Hookes Law
- If you strech something with a steadily increasing force, then the length with increase steadily also

(or ) Extension is prortional to load

# Refraction
- bending of waves

- changing direction as they enter a different medium

- waves travel slower in a shallower water
-  change in direction
- change in wavelength
- no change in frequency

Glass Block experiment

- air to glass - bends towards the normal
- glass to air - bends away from the normal

# total internal reflection

- only happens when light is coming out of something dense e.g water glass
- if angle is shallow enough ray won't come out at all
- it reflects back into the glass

#Diffraction
- spreading out of waves

# Space

- Planet - reflects light - non luminous
- Star - gives out light - luminous
- Solar system - collection of planets orbiting a star
- Galaxy - collection of stars and their solar systems
- Moon - heavenly bodies orbiting a star
- Asteroid - belt of rocks orbiting between mars and jupiter
- Meteors - asteroids knocked out of their orbits
-Comets - orbit sun, have eccentric orbits

First man in space - Uri Gargan - Russian
First man on moon - Neil Armstrong - American

Origins of universe

Big Bang
- all matter in universe was compressed into a very small space then exploded
- 15 billion years ago
- expansion is still going on

Steady State Therory
- Universe has always existed

Creation
- God created the universe

Satelites
- moon - natural satellities
- artifical satelites are created by humans to:

monitor weather
comunication - phone TV
space research e.g. Hubble telescope
spying

#Efficiency

Efficiency  = useful energy out / total energy input

-less than one
- or is as a percentage

Renewable / Non renewable

Non renewable
- will run out one day
- all do damage to the enviornment
- provide most of our energy

- coal
- oil
- natural gas
- nuclear fuels (uranium and plutonium

-Renewable
- will never run out
- do not damage the enviornment  (except visually)
- don't provide much energy
- unreliable - they depend on the weather

- wind
- waves
- tides
- hydroelectric
- solar
- geothermal
- food
- biomass (wool)

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