Physics

• Amplitude


  the height of wave crest that starts from the middle or the bottom

  • (for sound the larger the amplitude the louder the sound)
• Frequency

  Hertz (Hz - unit for frequency)

  frequency determines the pitch for sound

  frequency determines the color of light

  number of waves passing a fixed point per second
• Scalar quantities

  • have size but no direction
  • mass
  • distance
  • speed
  • energy
  • time
  • temperature
• Vector quantities

  • have both size and direction
  • weight
  • displacement
  • velocity (speed in a given direction)
  • force
  • acceleration
  • momentum
• Forces

  • water resistance
  • air resistance
  • push and pull
  • friction
  • tension
  • magnetic
  • electric static
  • gravitational pull
• Newtons first law

  the car below has a resultant force meaning the overall force acting on a object for example

  the cars friction is 3N and driving force is 5N, to solve this we would do 5-3=2N so it would be going 2N to the right because 5 is more than 2

  
• Balanced forces

  • zero resultant forces
  • velocity will not changes
  • if the object is moving it will continue to move at the same speed in the same direction (constant velocity)
  • object does not accelerate
• Unbalanced forces

  • non- zero resultant force
  • velocity changes (speed and/or direction changes)
  • the velocity of the object will depend on the size and direction of the resultant force
  • resultant forces acting in the same direction will need to be added and subtracted if acting in another direction
  • object speeds up and accelerates = right/ forwards
  • object slows down and decelerates = left/ backwards
• Energy being transferred in 5 ways:

  • mechanically
  • electrically
  • by heating
  • by radiation: light and sound
• Units of energy

  1KJ = x1000 to get J
• Efficiency

  energy supplied = useful + wasteful energy

  efficiency = useful energy divided by total energy supplied

  efficiency as a % = useful energy divided by total energy supplied x 100
• Energy transferred by heating

  1. convection
  2. conduction
  3. radiation
• Conduction

  takes place in solids as particles vibrate in a solid. energy is transferred from one end of a solid to another by the vibration of particles
• Convection


  takes place is fluids (liquids and gases) as particles can move and flow.
• Convection current

  1. liquid/gas is heated
  2. liquid/gas expands
  3. density of liquid/gas decreases
  4. warm liquid/gas rises
  5. cooler liquid/gas falls
  6. process repeats
• Radiation


  takes places in solids, liquids, gases and vacuums (a space). radiate means to spread out from hot source eg. sun, fire transfer energy by heating. thermal radiation is the transfer of energy by heating by infrared waves
• Thermal conductors


  materials that allow energy to be transferred by heating

  eg. metals, iron, copper, steel, aluminum

  used in cooking pots and heating filaments in kettles and heaters
• Thermal insulators

  • poor conductors
  • reduces energy transfer by heating
  • eg. solids that are non metals such as plastics, wood, felt, fur, wool
  • fiberglass are good insulators because they reduce energy transfer by conduction
  • trapped air is a good insulator because trapped air reduces energy by convection
  • a vacuum is a good insulator because they stop energy transfer by conduction and convection
  • used in cooking pots and vacuum flasks
• Surfaces and radiation: dark, matt surfaces in presence of heat

  • good absorbers, poor reflectors of radiation
  • they absorb radiation better than lighter surfaces
  • get warmer quicker than lighter surfaces
• Surfaces and radiation: light, shiny surfaces in presence of heat

  • poor absorbers, good reflectors of radiation
  • they reflect radiation better than darker surfaces
  • get less warm than darker surfaces
• Surfaces and radiation: dark, matt surfaces for hot objects

  • good emitters of radiation
  • emits more radiation than lighter surfaces
  • cools down quicker than lighter surfaces
• Surfaces and radiation: light, shiny surfaces for hot objects

  • poor emitters of radiation
  • emits less radiation than darker surfaces
  • cools down slower than darker surfaces
• Kinetic energy

  KE is the energy stored in moving objects

  KE = 0.5 x m x vsquared
• Gravitational potential energy

  GPE is stored in an object because of its position in the earths gravitational field.

  GPE = m x g (10) x h
• Work done


  moved a distance by a force in the direction of motion

  work done = force x distance
• Power: energy transfer


  power (w) = energy transferred divided by time
• Power: work done


  Power = work done divided by time
• Non- renewable energy resources

  • nuclear eg. uranium
  • fossil eg. coal, gas, oil
• What are x-rays used for?

  • detecting bone fractures
  • treating cancer
• How do you find this in minutes?

  1.50 = 90 because you have to do 1.50x60
• Conversion

  1. 1,000 millimeters (mm) = 1 meter.
  2. 100 centimeters (cm) = 1 meter.
  3. 10 decimeters (dm) = 1 meter.
• What is represented in a velocity time graph

  Displacement/ distance travelled
• Newtons first law

  objects will remain at rest, or move with a constant velocity, unless acted on by a resultant force
• Newtons second law

  • An object will accelerate (change its velocity) in response to a resultant force
  • The bigger this resultant force, the larger the acceleration
  • For a given force, the greater the object's mass, the smaller the acceleration experienced
• Newtons third law

  Whenever two objects interact, the forces they exert on each other are equal and opposite 
• to get an unit on its own to calculate it:

  
• What equation relates with thinking distance, stopping distance and braking distance


  stopping distance = braking distance + thinking distance
• Wind energy

  • used for generating electricity
  • renewable
  • no co2 produced
  • visual pollution
  • noise pollution
• Hydroelectric power

  • used to generate energy
  • water is renewable
  • no co2 produced
• Wave power

  • used to generate electricity
  • water is renewable
  • may cause harm to wildlife
  • no co2 produced