energy

• Work done


  The energy transferred when a force is used to move an object a certain distance
• Work


  Measured in Joules (J)
• Situations where work is done

  • Lifting a book against gravity
  • Sliding a book along a table against friction
• Calculating work done


  work done (J) = force (N) × distance moved (m)
• Simple machine


  Makes it easier to lift things, they reduce the force needed
• Force multiplier


  Uses a smaller input force (what you apply) to generate a larger output force (what is created)
• Increasing the distance from the pivot

  Less input force is needed to be used for the same output force as before
• Example of a force multiplier

  • Lever
• Longer lever


  Requires less input force than a shorter lever to produce the same output force
• What is temperature

  Measure of how hot or cold a substance is
• How do you measure temperature

  Measured with a thermometer, in degrees Celsius (°C)
• Thermal energy


  Depends on the individual energy of all the particles, measured in Joules (J)
• Larger volume of substance at lower temperature


  Can have more thermal energy than a smaller volume at higher temperature
• Faster moving particles


  Have more thermal energy
• Heating particles


  They begin to move more quickly
• Energy needed to increase temperature

  • Depends on mass of substance
  • What the substance is made of
  • How much temperature increase
• Radiation


  Method of transferring energy without the need for particles
• Example of radiation


  • Thermal energy from the Sun to Earth through space
• Infrared radiation


  Type of wave like light
• Hotter object


  Emits more infrared radiation
• Factors affecting radiation absorption and emission

  • Darker matte surfaces absorb and emit more
  • Shiny and smooth surfaces absorb and emit less, reflecting more
• Thermal imaging camera


  Can view the amount of infrared radiation being emitted
• Conduction


  Transfer of thermal energy by the vibration of particles, requires particles
• Particles colliding


  Transfer thermal energy
• Conduction in solids


  • Particles are close together and can collide often as they vibrate around a fixed point
• Metals as thermal conductors


  • Contain free-moving electrons
• High to low thermal energy store


  Thermal energy will be transferred
• Insulators


  Gases and liquids are poor conductors as their particles are spread out and do not collide often
• Convection


  Transfer of thermal energy in a liquid or gas, requires particles
• Convection process


  1. Heated particles spread out, become less dense, and rise

  2. More dense particles take their place at the bottom nearest the heat source, creating a convection current
• Convection cannot happen in a solid as the particles cannot flow, they can only move around a fixed point
• Conduction


  Transfer of thermal energy by the vibration of particles.
• Convection


  Transfer of thermal energy when particles in a heated fluid rise.
• Convection Current


  The movement of heated fluids where hot fluid moves upwards, and cold fluid moves downwards.
• Deform


  When an object is stretched or squashed, which requires work.
• Displacement


  The distance an object moves from its original position.
• Infrared Radiation


  Radiation given off by the Sun and other objects that brings about energy transfer.
• Input Force


  The force you apply to a machine.
• Output Force


  The force that is applied to the object moved by the machine.
• Lever


  A type of machine which is a rigid bar that pivots about a point.