topic 3

• what is the equation for gravitational potential energy 


  mass x gravitational field strength x height
• what is mass measured in

  kg
• what is gravitational field strength measured in

  n/kg
• what is height measured in

  metres
• what is the equation for kinetic energy

  1/2 x mass x velocity²
• what is meant by conservation of energy

  the toal amount of energy in a closed system remains constant , energy cannot be created or destroyed but it can change from one form to another
• what is waste energy

  the energy that is not used by the device for its desired purpose , or not converted into the desired form
• state 2 equations to calculate efficiency

  useful energy output / total energy input

  useful power output / total power output
• state the consequence for energy transfer of a material with high thermal conductivity

  the rate of energy transfer through the material is higher than for a material with a lower thermal conductivity
• do double glazed windows have a higher or lower thermal conductivity than single glazed windows 


  lower , meaning that less energy transfers through them
• state three methods of reducing heat loss in a building

  double glazing , loft and wall insulation , thicker walls
• how can you reduce unwanted energy transfer in a mechanical system

  reduce friction by lubricating moving parts
• how can the efficiency of a system be increased

  reducing waste output e.g by lubrication or thermal insulation ,

  recycling waste output e.g recycling waste thermal energy as input energy
• what is a renewable energy source

  an energy source which can be replenished as it is being used up