Physics 1

• The SI unit of energy is the joule (J)
• Heat transfer occurs when there is a temperature difference between two objects, with hotter objects losing heat and cooler ones gaining it.
• System


  A single object or group of objects that you're interested in
• Closed system


  A system where neither matter nor energy can enter or leave
• The net change in the total energy of a closed system is always zero
• Energy transfers


  1. Transferred into or away from a system

  2. Between different objects in the system

  3. Between different types of energy stores
• Energy stores


  • Buckets that energy can be poured into or taken out of
• Energy stores


  • Kinetic
  • Thermal
  • Chemical
  • Gravitational Potential
  • Elastic Potential
  • Electrostatic
  • Magnetic
  • Nuclear
• Objects with energy in the kinetic energy store


  • Anything moving
• Objects with energy in the thermal energy store


  • Any object, the hotter it is the more energy it has
• Objects with energy in the chemical energy store


  • Anything that can release energy by a chemical reaction, e.g. food, fuels
• Objects with energy in the gravitational potential energy store


  • Anything that has mass and is inside a gravitational field
• Objects with energy in the elastic potential energy store


  • Anything that is stretched (or compressed), e.g. springs
• Objects with energy in the electrostatic energy store

  • Anything with electric charge that is interacting with another electric charge
• Objects with energy in the magnetic energy store


  • Anything magnetic that is interacting with another magnet
• Objects with energy in the nuclear energy store

  • Atomic nuclei
• Energy transfers


  • Mechanically
  • Electrically
  • By heating
  • By radiation
• Energy transfer by heating


  • Energy transferred from a hotter object to a colder object
• Energy transfer by radiation

  • Energy from the Sun reaching Earth by light
• The conservation of energy principle: energy can be transferred usefully, stored, or dissipated, but can never be created or destroyed
• When energy is transferred between stores, not all of the energy is transferred usefully to the store that you want it to go to. Some energy is always dissipated when an energy transfer takes place.
• Kinetic energy


  Energy possessed by an object due to its motion
• Kinetic energy


  • A van of mass 2450 kg travelling at 40.0 m/s has 1,960,000 J of kinetic energy
• Gravitational potential energy


  Energy possessed by an object due to its position in a gravitational field
• Gravitational potential energy


  • A 50 kg mass lifted 2 m has 980 J of gravitational potential energy
• Gravitational potential energy


  • A flea jumping 10 cm has 0.049 J of gravitational potential energy
• Elastic potential energy


  Energy possessed by a stretched or compressed object
• Gravitational potential energy


  Energy stored in an object due to its position in a gravitational field
• Gaining gravitational potential energy

  1. Work is done to lift an object in a gravitational field

  2. This transfers energy to the gravitational potential energy store of the object

  3. The higher an object is lifted, the more energy is transferred to its gravitational potential energy store
• Amount of energy in an object's gravitational potential energy store


  Depends on the object's mass, height, and the strength of the gravitational field
• On Earth, the gravitational field strength is approximately 9.8 N/kg
• The principle of conservation of energy states that energy can never be created or destroyed, only transferred or transformed
• Elastic potential energy


  Energy stored in an object due to its deformation (stretching or squashing)
• Energy is transferred by the heater at the time of each temperature reading using the formula E = Pt, where t is the time in seconds since the experiment began
• The holes are a lot bigger than the thermometer, so you should put a small amount of water in with the thermometer to ensure it can measure the temperature of the black block
• There is no air around the black block, so it is not insulated
• The temperature change, ΔT, is how much the temperature has changed since the start of the experiment
• If you just want to compare the heat capacities, you should use identical masses of each material and identical methods for each material
• If you assume all the energy supplied by the heater has been transferred to the black block, you can plot a graph of energy transferred to the thermal energy store of the black against temperature
• The graph should be linear, but may start off curved. You don't need to worry about why this happens, just ignore the curved part of the graph