conservation of energy

• energy can be transferred between and held in different energy stores
• kinetic energy: movement energy, anything moving has energy in its kinetic energy store
• thermal energy: heat energy stored in the bonds of molecules in a substance
• chemical energy: anything that can release energy by a chemical reaction
• gravitational potential energy: anything in a gravitational field
• elastic potential energy :the energy stored in a stretched spring or elastic object
• electrostatic energy: two charges that attract each other, energy is released when the charges are separated
• magnetic energy: two magnets that attract or repel each other
• nuclear energy: atomic nuclei release energy from this store in nuclear reactions
• kinetic energy (J) = 1/2 x mass (kg) x speed (m/s)2
• GPE (J)= mass(kg) x gravitational field strength(N/kg) x height(m)
• energy can be stored, transferred between stores, and dissipated - but it can never be created or destroyed. The total energy of a closed system has no net change
• energy can be transferred between stores in 4 ways

  mechanically - a force acting on an object

  electrically - a charge doing work

  by heating - energy transferred from a hotter object to a colder object

  by radiation - energy transferred by waves
• energy is only useful when it is transferred from one store to a useful store.
• efficiency= useful energy output/ total energy input
• lubrication and thermal insulation are two ways to reduce unwanted energy transfers
• lubrication reduces energy transferred by friction
• insulation reduces the rate of energy transferred by heating
• non renewable energy resources are limited and cannot be replaced as quickly as they are used. They are fossil fuels and nuclear power which provide most of the world's energy.
• three main fossil fuels

  coal, oil, natural gas
• renewable energy resources that will never run our

  bio-fuels, wind, sun, hydro-electricity, tides