1 - Energy

• • Kinetic energy: energy stored in moving objects
  • Station objects have no kinetic energy

  Formula :

  Ek = 0.5 x mass x speed^2

  Ek: J

  Mass Kg

  Speed m/s

  
• • When we stretch a spring we’re applying a force to change

  the length of the spring (this is called doing “work”)

  • Elastic potential energy: putting energy into stretching 

  the spring which then stores the energy

  A) limit of proportionality

  B) directly proportional

  
• • Gravitational potential energy is the energy stored in an 

  object due to its position about the Earth’s surface 

  • This is due to the force of gravity acting on an object

  Formula:

  gravitational potential energy = mass x gravitational field strength x height

  
  

  Ep = J

  Mass = Kg

  g = N/kg

  h = m

  
• • Specific heat capacity: the amount of energy required to raise the temperature of 1kg of a substance by 1°C

  Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg °C) x Temp change (°C)

  kilojoules → joules (x1000)

  
• Types of Energy

  • Kinetic energy: energy stored in a moving object 
  • Gravitational potential energy: the energy stored due to an object's position

   above the ground 

  • Elastic potential energy: the energy stored in stretched spring

  Thermal Energy: the energy stored due to an object's temperature
• The law of conservation of energy: energy can be transferred usefully, stored or dissipated by it cannot be created of destroyed 

  • A system is an object, or a group of objects 
  • Closed System: no energy can enter or leave 
• Pendulum

  • Theres friction in the fixed point, as the pendulum passes through the air particles 
  • Friction causes energy to be transferred to thermal energy- the fixed point and air around the pendulum gradually get warmer 
  • These stores are less useful so the energy has been dissipated (wasted) - This will cause the pendulum to swing with less energy and eventually stop 

  
• Reducing Unwanted energy transfers:

  • can reduce unwanted energy transfers by reducing friction: use lubricant, remove air particles  
• Bungee Jumper:

  1. start of the jump all energy is in the gravitational potential store, as he falls energy is transferred from GPE to the kinetic store
  2. when rope starts to tighten, the kinetic energy store is at maximum- rope has fully extended and kinetic energy store is at 0, jumper is not moving
  3. rope then recoils and energy transfers from elastic potential to kinetic energy, the ascent- kinetic energy is transferred to GPE
  4. top of ascent, all energy is now in the GPE  
• Bungee Jumper

  • The jumper never returns back to the original position
  • This is because energy is dissipated as thermal energy (Due to friction with air a particles & Stretching effect in the bungee rope which is not fully elastic)
• • Work is done whenever energy is transferred from one store to another 
  • Mechanical work involves using a force to move an object 
  • Electrical work involves current transferring energy 

  Work done (J) = Force (N) x Distance (m)

  
• Power: is the rate at which energy is transferred or the rate at which work is done 

  • 1 watt is an energy transfer (or work done) of 1 J per second

  power (w) = energy transferred (J) / time (s)

  power (w) = work done (J) / time (s)

  
• Efficiency: a measure of performance and effectiveness of a 

  system or component 

  Efficiency = useful output energy / total power input

   

  (output/total input)

  
• Thermal conductivity:  the ability of a material to conduct heat from one side to the other

  Reducing thermal energy transfer from a home:

  • Construct building using materials with low thermal conductivity 
  • Build the house with thick walls (reduced the rate of thermal energy transfer) 
  • Double glazed windows has low thermal conductivity 
  • Loft insulation (low thermal conductivity)
• Required Practical- Specific Heat Capacity

  1. place beaker of oil and record the mass using a balance, place thermometer and an immersion heater into the oil. Read the starting temp of oil
  2. wrap the beaker in insulation foam to reduce thermal energy transfer to surroundings
  3. connect a joules meter to immersion heater (tells us how many joules of electrical energy passes into immersion heater)
  4. time for 30 mins then read total number of joules or energy and final temp
  5. then calculate specific heat capacity (rearrange formula)

  c = change in thermal energy/ mass x change in temp

  
• Required Practical- Specific Heat Capacity

  Sources Of Inaccuracy:

  Thermal energy passing out the beaker and into the air 

  • Use an insulator with a low thermal conductivity 

  Not all thermal energy passing into the oil 

  • Ensure that immersion heater is fully submerged 

  Incorrect reading of thermometer 

  • Use an electronic temperature probe
•  Nuclear power is non renewable, nuclear power plants run on uranium and plutonium 

  Advantages 

  • Releases no carbon dioxide- doesn’t affect climate
  • Reliable, generates a lot of electricity

  Disadvantages 

  • Highly dangerous radioactive materials- risk to the environment 
  • Decommission takes many years and is expensive
  • Generates radioactive waste and must be stored for thousands of years before it’s safe
• Uses of energy: transport, generating electricity & heating 

  Main fossil fuels: coal, oil and gas 

  
  

  Advantages 

  • Reliable, they always provide energy when needed 
  • Release a great deal of energy 
  • abundant and relatively cheap
  • Extremely Versatile- use them for a lot

  Disadvantages 

  • Release huge amounts of carbon dioxide
  • Non- renewable not being replenishing, will one day run out
  • Releases pollutants eg: diesel- carbon dioxide and nitrogen oxide 

  Coal- sulphur dioxide leads to acid rain 
• The UK Energy Mix

  Switch from coal to gas

  • Burning gas generates less carbon dioxide than burning coal. This contributes to less climate change 
  • Gas-fired power stations are flexible. They can be switched on quickly during periods of high demand (short start-up time)- coal fired power stations take a long time to start up 

  Switch to renewables 

  • Windpower, solar power and biofuels.  Reliability is low 

  Need a base load (constant supply of electricity that's on all the time) - nuclear power is ideal 

  • Gas fired power stations to provide emergency power in times of peak demand
• Renewable energy resources: is one that is being (or can be) replenished as it is used 

  Advantages 

  • Never Run Out 
  • Once in place, do not add any CO2
  • Geothermal- uses heat from earth (reliable)
  • Wave power - reliable 
  • Biofuels- produced from plant materials (no extra carbon dioxide) - use to power vehicles 

  Disadvantages 

  • Wind power & solar power are not reliable (wind and sun)
  • Hydroelectric power- reliable but habitats are destroyed, only useful in countries that have lots of rivers  
  • Wave power - causes harm to nature 
  • Biofuels- if land is for fuel the price of food/crops will increase