1 - Energy

• What is kinetic energy?

  
  

  What is the equation for kinetic energy?


  Kinetic energy is the energy stored in moving objects.

  
  

  Ek = 0.5 x m x v^2

  J = 0.5 x kg x (m/s)^2
• What is elastic potential energy?

  
  

  What is the relationship between the extension and force applied? What happens if we apply too great a force?

  
  

  What is the equation for elastic potential energy?


  Elastic potential energy is the store of energy after doing work in a stetched spring.

  
  

  The force applied (N) is directly proportional to the extension (m) but if we apply too great a force, the spring is stretched beyond the limit of proportionality and will not return back to the original length if the force is removed.

  
  

  Ee = 0.5 x k (N/m) x e^2 (m)
• What is gravitational potential energy?

  
  

  What is the equation for gpe?


  Gravitational potential energy is the energy stored in an object due to its position above the Earth's surface.

  
  

  Ep = m (kg) x g (N/kg) x h (m)
• What is specific heat capacity?

  The amount of energy required to increase the temperature of 1kg of a substance by 1°C.
• What is the equation for specific heat capacity?


  Change in thermal energy = mass x specific heat capacity x change in temperature

  
  

  
  

  ΔE = m x c x Δθ
• What is the law of conservation of energy?

  Energy cannot be created or destroyed.
• What is a system? What happens in a closed system?

  .An object or group of objects. In a closed system, no energy can enter or leave.
• How can we reduce unwanted energy transfers by reducing friction in the case of a pendulum?

  By using a lubricant, or by removing the air particles around the pendulum.
• Why does a bungee jumper not return to the original height?

  Energy is dissipated as thermal energy due to friction with air particles and stretching effects because the rope is not fully elastic.
• What happens when work is done?

  Energy is transferred from one store to another.
• What is mechanical work?

  Using a force to move an object.
• What is electrical work?

  When a current transfers energy.
• What is the equation for work done?

  Force (N) x Distance (m)
• What is power?

  Power is the rate at which energy is transferred or the rate at which work is done.
• What are the 2 equations for power?

  - power (W) = energy transferred (J) / time (s)

  
  

  - power (W) = work done (J) / time (s)
• What is the equation for efficiency?

  Efficiency (%) = (useful energy output / total energy input) x 100
• How can we increase the efficiency of a pan on a hob?

  - wider base

  - lid

  - heating element inside water

  - plastic walls and lid (kettle) instead of metal
• What affects the cooling of a nuilding?

  - thermal conductivity of the materials
• Why is the cavity between the external brick wall and the internal breezeblock wall packed with insulating material?

  This insulating material has a very low thermal conductivity so less thermal energy is lost through the walls.
• How can we reduce the loss of thermal energy of a house?

  - double glazed windows (lower thermal conductivity)

  - loft insulation

  - build house with thicker walls

  - wall insulation
• Decribe a method to determine the shc of a material.


  1) Record the mass of the material with a balance.

  2) Place a thermometer and an immersion heater into the substance.

  3) Record this starting temperature.

  4) Wrap the substance with an insulating material to reduce loss of heat to surroundings.

  5) Connect a joulemeter and powerpack to the immersion heater.

  6) Turn on and leave for 30min.

  7) Read the number of joules of energy that passed into the immersion heater and final temperature of substance.

  
  

  ΔE (J) = m (kg) x c (J/kg°C) x Δθ ) =>

  
  

  c = ΔE / (m x Δθ )
• What are the sources of inaccuracy in this experiment?

  - heat passing out of substance (use insulating material)

  - not all thermal energy passed into substance (ensure immersion heater is fully submerged)

  - incorrect thermometer reading (use an electronic temperature probe)
• Describe a method to investigate the effect of different thermal insulators.

  1) Place a smaller beaker inside a larger beaker.

  2) Use a kettle to boil some water and transfer 80cm3 of the hot water into the small beaker.

  3) Use a piece of cardboad as a lid for the large beaker (with a hole for a thermometer).

  4) Place a thermometer into the hole.

  5) Record starting temperature.

  6) Record the temperature of the water every 3mins for 15mins.

  7) Repeat experiment with the same volume of hot water but with an insulating material, e.g. bubble wrap, to fill the gap between the 2 beakers.

  8) Repeat again with a different insulating material, e.g. wool
• How can we also investigate the effect of different thicknesses of the same inslating material?

  1) Fill a beaker with 80cm3 of hot water.

  2) Measure the temperature of the water every 3mins for 15mins.

  3) Repeat experiment but with added layers of insulating material each time.
• What are 3 uses of energy?

  - powering transport

  - generating electricity

  - heating
• What are the 3 main fossil fuels?

  - coal

  - oil

  - natural gas
• What are the advantages of fossil fuels?

  - reliable

  - release a lot of energy

  - abundant

  - cheap

  - versatile
• What are the disadvantages of fossil fuels?

  - burning fuels releases CO2

  - non-renewable

  - can release other pollutants
• How do nuclear power plants work?

  Nuclear power plants run on uranium and plutonium.
• What are the benefits of using nuclear power?

  - non-renewable

  - no CO2 emissions

  - extremely reliable
• What are the cons of using nuclear power?

  - contain highly dangerous radioactive materials (peak if released into the environment)

  - decommissioning a plant takes many years and is expensive

  - generates bare amounts of highly dangerous radioactive waste
• What is the most abundant energy source in the UK?

  Coal init
• What pros did the Uk have for switching from coal to gas?

  - less CO2 emissions

  - gas-fired power stations are flexible (short start-up time)
• In the 70s, why didn't politicians want to switch to using renewable sources of energy?

  - did not see climate change as a big issue

  - energy from fossil fuels was cheap (economic factor)
• What would be the most ideal source of energy for the UK?

  - UK has great location for windpower
• How can we solve the problem of the reliability of renewable energy resources?

  - need a base load (constant supply of electricity all the time); best is nuclear power for this

  - use gas-fired power stations in times of peak demand (short star-up time)
• What is a renewable energy source?

  A renewable energy resource is one that is being (or can be)

  replenished as it is used.
• Give 7 examples of renewable resources.

  - wind power

  - solar power

  - hydroelectric power

  - biofuels

  - tidal power

  - geothermal

  - wave power
• What are the advantages of renewable energy sources?

  - will nerver run out

  - no CO2 emissions => no contribution to climate change
• What are the disadvantages of renewable energy sources?

  - wind / solar power are not reliable

  - habitats are destroyed when dams are built and valleys are flooded with HEP

  - HEP only useful in ends with bare rivers

  - biofuel could increase prices for food as limited land is instead used to grow crops for fuel