P1

• Conservation of energy

  Never created or destroyed, only transferred between different forms and objects
• Forms of energy


  • Thermal or internal energy
  • Kinetic energy
  • Gravitational potential energy
  • Elastic potential energy
  • Chemical energy
  • Magnetic energy
  • Electrostatic energy
  • Nuclear energy
• Energy transfer

  1. Mechanical

  2. Electrical

  3. Heating

  4. Radiation (light or sound waves)
• System


  Collection of matter
• Open system


  Can exchange energy with the outside world
• Closed system

  Separate from the outside world, no exchange of matter or energy
• Work done

  Energy transferred
• Types of work done

  • Mechanical
  • Electrical
• When coal is burned the chemical energy is transferred by heating to the thermal energy store of the coal. Hot coals and flames transfer energy to the surroundings by heating and radiation.
• Kinetic energy


  The energy that an object possesses due to its motion
• Kinetic energy


  • Depends on an object's speed
  • Depends on an object's mass
• Faster an object is moving

  More kinetic energy it will have
• More mass an object has

  More kinetic energy it will have
• Calculating kinetic energy


  1. Use the equation: E_k = 1/2 m v^2

  2. E_k = kinetic energy

  3. m = mass (in kg)

  4. v = velocity (in m/s)
• Gravity


  A force of attraction between two objects, with the size of the force depending on the mass of the objects and the distance between them
• For small objects like apples or buildings, the gravitational force of attraction is tiny as they have relatively low masses
• For very large objects that are far away like Jupiter, the gravitational force is also tiny due to the large distance
• For very large objects that are close by, such as the Earth or the Moon, gravity is felt more strongly and has a big influence on nearby objects
• Gravitational field


  The field of influence around an object
• Gravitational field strength


  The strength of the gravitational field, denoted by the letter g
• The gravitational field strength on Earth is around 9.8 Newtons per kilogram
• Weight


  The force of attraction experienced by an object in a gravitational field
• Calculating weight

  Mass x Gravitational field strength
• Weight and mass are different in physics, where mass is an intrinsic property of an object and weight is the force acting on it in a gravitational field
• Gravitational potential energy


  The energy an object has due to its position in a gravitational field
• Calculating gravitational potential energy

  Mass x Gravitational field strength x Height
• Gravitational potential energy is measured in Joules
•  Mass is measured in kilograms (kg) 
•  Weight is measured in newtons (N) 
• The moon's gravitational field strength is 1.6 N/kg
• 1. As an object rises, KE is converted to GPE
  2. As an object falls, GPE is converted to KE 
  3. KE lost = GPE gained and KE gained = GPE lost
• Internal energy

  The total energy that's stored by the particles making up a substance or system
• Internal energy

  • Made up of potential energy stores and kinetic energy stores
  • Potential energy stores (gravitational and elastic potential) are not related to temperature
  • Kinetic energy is the movement energy of the particles and is important for temperature
• Heating up a substance

  Transfers energy to the kinetic energy store of the particles, increasing their internal energy
• Temperature


  A measure of the average internal energy of a substance
• Specific heat capacity

  The amount of energy needed to raise the temperature of one kilo of a substance by one degree Celsius
• Water requires 4,200 joules of energy to warm one kilo by one degree Celsius
• One kilo of mercury can be heated by one degree Celsius with only 139 joules of energy
• Calculating change in internal energy

  Change in internal energy = mass x specific heat capacity x change in temperature
• Specific heat capacity is the amount of energy required to raise the temperature of 1 kg of a substance by 1 °C.