Physics energy

• Kinetic energy


  The energy stored in moving objects
• Kinetic energy

  1/2mv squared
• A car runs on petrol (chemical energy)

  Some of the energy is converted to kinetic energy as the car moves
• Energy can be transferred, stored or dissipated, but it cannot be created or destroyed
• Closed system


  No energy can enter or leave the system
• Lubricant such as oil on the fixed point or removing air particles can reduce friction in the pendulum
• Mechanical work


  • Using a force to move an object
• Work done


  Force (N) X distance (M)
• Power


  The rate at which energy is transferred or the rate at which work is done
• Calculating power


  1. Energy transferred (J) ÷ Time (S)

  2. Work done (J) ÷Time (S)
• Incandescent bulbs vs LED bulbs

  • Incandescent bulbs are less efficient, with most energy transferred to thermal energy rather than light
  • LED bulbs are more efficient, with a greater percentage of energy transferred to light
• Thermal conductivity


  How well a material conducts heat
• Factors that affect the cooling of a building

  • Thermal conductivity of the walls
  • Thickness of the walls
• Single glazed windows have a high thermal conductivity, allowing a lot of thermal energy to pass through
• Double glazed windows have a lower thermal conductivity, reducing the amount of thermal energy that can pass through
• Loft insulation also has a low thermal conductivity, reducing the rate at which thermal energy passes through the roof
• Constructing a building using materials with low thermal conductivity and thick walls can reduce the rate of thermal energy transfer from the building
• Main fossil fuels used for energy

  • Coal
  • Oil
  • Gas
• Advantages of using fossil fuels

  • Reliable
  • Release a great deal of energy
  • Cheap
• Disadvantages of using fossil fuelsHuge amount of CO2, contributing to climate change

  • Non-renewable
  • Can release pollutants