Physics

• Work done = force x distance moved in direction of force
• Energy can be transferred between objects by work done, heating or cooling, and electric current.
• Energy is the ability to do work.
• Potential energy is stored energy that can be converted into kinetic energy or other forms of energy.
• Kinetic energy is the energy an object has due to its motion, measured by half mass times velocity squared (KE=1/2mv^2).
• In an isolated system (no transfer of matter), energy cannot be created or destroyed but only transformed from one form to another.
• Heat capacity is defined as the quantity of heat required to raise the temperature of a substance by one degree Celsius.
• The energy stored in an object depends on its mass and speed.
• Kinetic energy (KE) is the energy that an object has because it is moving.
• Potential energy (PE) is the energy that an object has due to its position or condition.
• Heat transfer occurs when there is a temperature difference between two objects.
• What is gravitational potential energy?


  it is energy that an object has depending on its height, the work done against the force of gravity
• What is the conservation of energy?


  Energy cannot be created or destroyed, only transferred
• What is a closed system?

  A system where neither matter nor energy can enter or leave
• What is work done?

  energy transferred when a force moves an object
• What is the formula for work done?


  Work done (J) = Force (N) X displacement in the force's direction (m).

  W = Fs
• How is the work done to overcome friction transferred?

  as thermal energy
• What is the formula for gravitational potential energy?


  Gravitational potential energy (j) = mass (kg) X gravitational field strength (N/kg) X height (m)

  E = mgh
• What is the formula for CHANGE in gravitational potential energy?


  ΔE = mgΔh

  Change in energy (J) = mass (kg) X gravitational field strength (N/kg) X change in height (m)
• What is the formula for kinetic energy?


  KE = 1/2mv^2

  Kinetic energy (J) = 1/2 X mass (kg) X velocity(m/s)^2
• What is kinetic energy store?


  the energy inside a moving object
• What is elastic potential energy?

  energy stored in an elastic object when work is done on it to change its shape
• What is the formula for elastic potential energy?

  PE = 1/2ke^2

  Potential energy = 1/2 X spring constant (N/m) X extension (m)^2
• What is useful and wasted energy?

  Useful energy - energy transferred to where it is needed for its purpose

  Wasted energy - the excess energy that isn't usefully transferred, usually to the surroundings as heat from friction
• What is efficiency?


  useful energy transferred as an output / total energy inputted

  
  

  No energy can be more than 100% efficient
• How can machines be made more efficient?

  lubricate moving parts to reduce friction

  use wires with as little resistance as possible

  streamline the shapes of objects to make them more aero/hydrodynamic

  tighten loose parts to reduce vibration
• What is power?


  the rate at which energy is transferred/work is done
• What is the formula for power?

  P = W/t

  Power (W) = work (J) / time (s)
• What is wasted power?

  total power in - useful power out
• What are conductors and insulators?

  Conductors let energy pass through easily while insulators slow it down/stop it entirely
• What factors affect insulators?

  temperature difference across the material

  thickness of the material

  thermal conductivity of the material
• What is infrared radiation?

  A type of radiation that all energy that all objects emit and absorb

  the hotter an object is, the more infrared radiation it emits in a given time
• What is blackbody radiation?

  Radiation emitted by a body that absorbs all the radiation incident on it
• How does infrared radiation apply to temperature?

  If an object absorbs infrared radiations more than it emits it, its temperature increases
• What factors heat the Earth?

  The absorption of infrared radiation from the sun and the emission or radiation from the Earth's surface and atmosphere
• What is specific heat capacity?

  The amount of energy required to increase the temperature of 1kg of a substance by 1°C
• What is the formula for specific heat capacity?

  ΔE = mcΔθ

  Energy transferred (J) = mass (kg) x specific heat capacity (J/kg°C) x temperature change (°C)
• How can you rate of reduce energy transfer fromhouses?

  loft insulation

  cavity wall insulation

  double glazed windows

  aluminium foil behind radiators

  external walls with thicker bricks
• What are biofuels?


  Renewable fuel resources taken from living or recently living organisms
• How do wind turbines generate electricity and what are their shortcomings?

  wind causes the blades to turn which turns a turbine which turns a generator to generate electricity

  
  

  However, they are unreliable as when their is far too little or too much wind, they won't work

  They require lots of maintenance

  They are big, loud and eyesores