1.1 Energy

• What is the equation for kinetic energy?

  $\frac{1}{2} m v^2$
• What are the SI units for kinetic energy?

  Energy (J), Mass (kg), Velocity (m/s)
• What is the equation for elastic potential energy?

  $\frac{1}{2} k x^2$
• What are the SI units for elastic potential energy?

  Energy (J), Spring Constant (N/m), Extension (m)
• What is the equation for gravitational potential energy?

  E=mgh
• What are the SI units for gravitational potential energy?

  Energy (J), Mass (kg), Gravitational Field Strength (N/kg), Height (m)
• What is the definition of 'Specific Heat Capacity'?

  Energy needed to raise 1 kg by 1°C
• What are the units for Specific Heat Capacity?

  J/°C/kg
• What is one equation for power?

  Power = energy transferred/time
• What is another equation for power?

  Power = work done/time
• What are the SI units for power?

  Energy (J), Work Done (J), Time (s)
• What is the definition of 'Power'?

  Rate at which energy is transferred
• What is the unit of power?

  Watt (W)
• Describe the energy changes when a ball is thrown upwards.

  • Upwards: KE is converted to GPE
  • Peak: Maximum GPE, zero KE
  • Downwards: GPE is converted to KE
• Describe the energy transfers for a bungee jumper.

  • Falling: GPE is converted to KE
  • Cord tightens: KE is converted to EPE
  • Lowest point: Initial GPE equals stored EPE
• Why does a bungee jumper slow down when the cord stretches?

  KE decreases as it converts to EPE
• What are the different stores of energy?

  1. Kinetic Energy
  2. Gravitational Potential Energy
  3. Elastic Potential Energy
  4. Chemical Energy
• What does the law of energy conservation state?

  Energy cannot be created or destroyed
• What happens to the total energy of a kicked ball without external forces?

  The total energy remains constant
• What is waste energy?

  Energy not used for its intended purpose
• What energy changes occur in a filament light-bulb?

  • Electrical energy is converted to light energy
  • Electrical energy is converted to heat energy
  • Light is useful; heat is waste energy
• What is the equation for efficiency using energy transfer?

  Efficiency = Useful Output Energy / Total Input Energy
• What is the equation for efficiency using power output?

  Efficiency = Useful Power Output / Total Power Output
• How can the efficiency of a system be increased?

  1. Reduce waste output (lubrication, insulation)
  2. Recycle waste output (thermal waste as input)
• What is the consequence of high thermal conductivity in materials?

  Higher rate of energy transfer through material
• Do double-glazed windows have higher or lower thermal conductivity than single-glazed windows?


  Lower thermal conductivity
• What factors affect the rate of cooling of a building?

  • Thickness of the walls
  • Thermal conductivity of the walls
• What are methods to reduce heat loss in a building?

  1. Double glazing
  2. Loft and wall insulation
  3. Thicker walls
• How can the efficiency of a mechanical machine with moving parts be improved?

  Lubricate moving parts to reduce friction
• How can the efficiency of boiling water in a pan be improved?

  Place a lid on the pan to reduce heat loss
• How can the efficiency of a radiator be improved?

  Install metal foil sheets behind the radiator
• What is a renewable energy resource?

  An energy source that can be replenished
• What is one advantage of generating power using gas rather than coal?

  Gas power stations have short start-up times
• What is another advantage of using gas over coal for power generation?

  Lower emissions of carbon dioxide
• State two disadvantages of using renewable energy resources.

  Supply is uncertain and less efficient
• What are the environmental impacts of burning fossil fuels?

  Contributes to greenhouse effect and acid rain
• What is one advantage of fossil fuels as an energy resource?

  Reliable and can generate power anytime
• Name two more advantages of fossil fuels.

  Produces large amounts of energy, cost-effective
• State three advantages of nuclear power.

  Large energy, no greenhouse gases, low fuel costs
• What is a disadvantage of nuclear power?

  Produces harmful nuclear waste needing storage