Key Terms

• Closed System

  A system that experiences no net change in its total energy when energy transfers occur within it.
• Conservation of Energy

  The law that energy can be transferred, dissipated, or stored but never created or destroyed.
• Efficiency

  The ratio of useful output energy to total input energy.
• Elastic Potential Energy


  The store of energy that stored or compressed objects experience. It is directly proportional to the stiffness constant and to the square of the extension or compression.
• Fossil Fuels

  Coal, oil and gas
• Gravitational Potential Energy

  The store of energy that all raised matter has. It is directly proportional to the mass of the object, the height that it is risen , and the gravitational field strength at that point.
• Joule (J)


  Unit of energy. Equal to the work done when a force over 1 Newton acts over a distance of 1 metre.
• Kinetic Energy

  The store of energy that all moving matter has. It is directly proportional to the object's mass and the square of it's velocity.
• Power

  The rate at which energy is transferred, or at which work is done.
• Renewable Energy Resource

  An energy resource that can be replenished whilst it's being used so it never runs out.
• Specific Heat Capacity

  The amount of energy required to raise 1Kg of a substance by 1 degree celcius.
• Spring Constant

  A measure of a Spring's stiffness. The greater the force, the greater the force required to stretch or compress a spring by a given distance.
• System

  A single, or group of, object(s).
• Thermal Conductivity

  The higher this value is for a given material, the higher the material's rate of energy transfer via conduction will be.
• Waste Energy

  Energy that isn't usefully used for the purpose of the system.
• Watt (W)

  Unit of power. One watt is equal to one joule of work being done per second (J/s).
• Work Done

  The energy transferred when a force acts over a distance.