Physics

• Energy 


  The capacity of doing work
• Energy store:


  Kinetic energy

  Thermal energy

  Gravitational energy

  Elastic energy

  Chemical energy

  Nuclear energy

  Magnetical energy

  Electro-static energy
• Transferring energy


  Electricity

  Wave

  Mechanical

  Thermal/heating
• Measurement for Energy


  Energy is measured in joules (j)
• Law of conservation of energy


  Energy cannot be created or destroyed it can only be transferred to another energy store
• Energy transfer in a computer

  Electrical energy 200J ->computer ->Light and sound 120J

  Thermal -> 80J
• Wasted Energy


  The reason why energy is wasted is because of friction. Wasted energy is dissipated into our environment, increasing the thermal energy store.
• Useful energy


  Is transferred where its wanted in the way it wanted.
• Wasted energy


  Energy that is not usefully transferred
• Work done


  When an object is moved by a force, work is done on the object by the force.
• Calculating work done


  Work done = Force x Distance moved
• Gravitational potential energy (GPE)


  When an object is lifted, energy is transferred from whatever is doing the lifting to the object
• Calculating Gravitational potential energy

  Mass x gravitational field strength x height
• Gravitational field strength for earth

  9.8
• Kinetic energy


  The energy an object has because of its motion
• Calculating kinetic energy


  Kinetic energy = 0.5 x mass x velocity squared
• Elastic potential energy


  Energy stored in an object that has been stretched or squashed
• Calculating elastic potential energy

  Elastic potential energy = 0.5 x spring constant x extension squared
• Calculating Efficiency


  Efficiency = Useful output energy ÷ Total input energy
• Power


  Power tells you the rate of energy transfer. The more powerful a transfer is, the faster the rate at which energy is transferred.
• Calculating Power


  Power (Watts) = Energy transferred (Joules) ÷ Time taken (seconds)