topic 3 - conservation of energy

• what is the equation for kinetic energy?

  0.5 x mass (kg) x velocity (m/s)
• what is conservation of energy?

  Energy cannot be created or destroyed, only transferred or transformed.

  • total amount of energy in a closed system remains constant
• describe the energy changes involved when a ball is thrown upwards, then returns to starting position

  • upwards: KE converted to GPE
  • peak: maximum GPE, zero KE
  • downwards: GPE converted to KE
• describe the energy changes that occur in a filament light - bulb

  • electrical energy transferred into light and heat energy
  • light is a useful energy form, heat is waste energy
• describe energy transfers for a bungee jumper

  when falling: GPE converted to KE

  cord tightens, KE converted and stored as EPE

  lowest point: jumper's initial GPE equals the EPE stored in the coil
• explain why a bungee jumper slows down once cord begins to stretch

  • Kinetic energy decreases since it is converted to elastic potential energy
  • KE is proportional to velocity squared, as KE decreases, so does velocity
• 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 output energy / total input energy

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

  • 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 less energy transfers through them
• 3 methods of reducing heat loss in 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
  • recycling waste output
• what is a renewable energy resource?

  • energy source which can be replenished as it is being used up
• 4 examples of renewable energy resources

  1. wind energy
  2. hydro - electricity
  3. tidal energy
  4. solar energy
• give an example of a non renewable energy resource

  • fossil fuels
• advantages of generating power using gas rather than coal?

  • flexible generation
  • lower emissions of carbon dioxide
• 2 disadvantages of renewable energy

  • renewable fuel often produce less energy per kg
  • output often determined by external factors, so supply is uncertain
• explain the environmental impacts of burning fossil fuels

  • carbon dioxide contributes to the greenhouse effect, causing global warming
  • sulphur dioxide leads to acid rain - can damage buildings and crops
• 3 advantages of fossil fuels as an energy resource

  1. reliable
  2. produce large amounts of energy per kg
  3. still relatively abundant, so cost effective
• 3 advantages of nuclear power

  1. low fuel costs
  2. no greenhouse released
  3. large amounts of energy per kg of fuel
• 3 disadvantages of nuclear power

  1. non renewable
  2. risk of nuclear accidents
  3. produces nuclear waste
• give examples of social factors to consider in energy production

  • visual pollution
  • sound pollution
• how does hydroelectric power produce energy

  • rainwater collects behind a dam
  • this water is released - used to turn a turbine
  • turbine turns a generator which produces electricity
• disadvantages of using biofuels

  • reduces land available for food crops
  • Habitat destruction
  • plants burned/decay - release carbon dioxide
• advantages of tidal energy sources

  • no greenhouse gases
  • fairly reliable - tide occurs twice a day
  • cheap to run as tides are natural, so free
• disadvantages of hydroelectric power

  • dam may cause flooding
  • cost a lot to install required infrastructure
• advantages of solar panels

  • don not harm environment
  • renewable
  • can be used in remote areas