P1

• Potential energy


  Potential energy is the energy stored in an object based on : position, properties and forces acting on it.
• Gravitational potential energy


  The energy of an object due to its position above the earths surface.

  This is due to gravity.
• Elastic potential energy


  The energy an object stored in an elastic object as a result of a force.
• Gravitational potential energy word equation (Units)

  GPE (J) = Mass (kg) x Gravitational field strength (N/Kg) x Height (m)
• Elastic potential energy word equation (Units)

  EPE (J) = 1/2 X Spring constant (N/m) x Extension (m)
• Elastic potential energy symbol equation 


  Ee = 1/2 x k x e2
• Gravitational potential energy symbol equation 


  Ep = m X g X h
• Kinetic energy


  Energy stored in moving objects.
• Kinetic energy word equation

  Kinetic energy = 0.5 x Mass (kg) x Velocity squared (m/s)
• Kinetic energy symbol equation


  Ek = 0.5 x m x v^2
• When we stretch a spring we are applying a force to change its length.

  Applying a force like this is called doing 'work'

  We are putting energy in to stretch the spring.This energy is then sored as elastic potential energy in the stretched spring.
• Law of conservation of energy

  Energy can be transferred usefully, stored or dissipated. However it cannot be created or destroyed.
• System

  Object or group of objects.
• Closed system


  System in which energy transfers cannot take place
• Work done

  When energy is transferred from one store to another
• Mechanical work

  Force is used to move an object
• Electrical work

  Current transfers energy
• Work done formulae

  Work done (J) = Force (N) x Distance (m)
• Energy can be transferred by:

  Heating

  Waves

  Electric currents

  By a force moving an object
• Work done t overcome friction, transfers energy to the thermal stores of the objects and the surroundings.
• Useful energy - energy transferred to where it is wanted in the way that it is wanted.
• Wasted energy - energy that is not usefully transferred.
• Improving efficiency


  Friction = Lubricated moving parts

  Resistance in wire = use wires with as little electrical resistance

  Air resistance = Streamline the shapes of moving objects

  Sound = Cut out noise (Tighten loose parts)
• Thermal energy

  Energy stored in object due to its temperature.
• w= mg
• Weight= mass x gravitational field strength
• Object projected upward

  KE decrease

  GPE increase
• A moving object colliding with a wall


  KE dissipated into wall

  Sound energy release
• Change in thermal energy = mass x specific heat capacity x change in temp.
• Specific heat capacity


  amount of energy required to increase 1kg of a substance by 1 degree
• Power = energy transferred / time
• Power = work done / time
• Energy cannot be created or destroyed