Topic 3: Conservation of Energy

• An object at any height will have energy in its gravitational potential energy (GPE) store. The higher the change in height when an object falls the greater the GPE
• Moving objects have kinetic energy (KE) which is determined by its speed and mass. The greater mass and speed the more KE
• Conservation of Energy - energy cannot be created or destroyed, only transferred, stored and dissipated
• Energy Changes:

  • Ball Up Slope - ball does work against gravity so energy is transferred mechanically from KE to GPE
  • Bat Hitting Ball - bat KE is mechanically transferred to ball KE, surrounding thermal stores and sound
  • Rock Falling Off Cliff - gravity does work on rock so rock accelerates constantly with GPE mechanically transferring to rock KE
  • Slowing Car - car KE mechanically transferred via friction and heat to the thermal energy of car and road
  • Kettle Boiling Water - energy transferred electrically to kettle then by heat to thermal store of water
• A closed system has no net change in energy as no energy is lost or gained
• Mechanical transfers mean frictional forces like air resistance and moving parts rubbing will transfer energy to the object and surrounding thermal stores which is wasteful.

  This can be prevented by lubrication and thermal insulation
• Lubrication:

  • usually liquids like oil
  • coat objects by easily flowing between
  • reduces contact and friction
• Thermal Insulation (Houses):

  • Conduction - transfers energy through an object
  • houses must have low thermal conductivity to retain heat
  • Cavity Walls/Windows - air gap between walls and (double-triple glazed) windows reduces conduction
  • thick walls with foam
• Non-Renewable Energy:

  • Fossil fuels are cheap to extract and build energy plants for but contribute to global warming via the greenhouse effect
  • Nuclear energy needs uranium/plutonium and the waste is toxic to the environment for years which makes it difficult to dispose of
  • Sulfur dioxide from burning fossil fuels causes acid rain
• Renewable Energy:

  • Bio Fuels - carbon neutral and fairly reliable but is expensive and takes a lot of space
  • Wind - no pollution and running costs are minimal but are noisy and spoil views
  • Solar - no pollution or running costs but can't be used at night or in cloudy dark counties
  • Hydro Electricity - no pollution and can respond to immediate demand but is expensive to build and destroys whole valleys
  • Tide - no pollution and cheap to maintain but effects boat access and spoil views