OCR GCSE Physics Notes | P7

  • Law of conservation of energy: energy cannot be created or destroyed, only transferred (usefully or wastefully).
  • Work done: energy transferred.
  • Chemical energy: stored in batteries/ muscles.
  • Gravitational potential energy: energy transferred in a falling object.
  • Kinetic energy: energy transferred in a moving object.
  • Elastic potential energy: energy transferred in a stretched object.
  • Energy transfers in a kettle: electrical, thermal, sound, kinetic.
  • Energy transfers in a calculator: chemical, light.
  • Energy transfers in a tennis ball dropped: gravitational potential to kinetic.
  • Heating an object: particles gain more kinetic energy, to overcome its specific heat capacity.
  • Work done = force x distance.
  • Ek = 0.5mv2
  • Ep = mgh
  • Ee = 0.5ke2
  • E: energy (J), m: mass (kg), v: speed (m/s), g: 9.8m/s2, h: height (m), k: spring constant, e: extension (m), P: power (W).
  • E = Pt
  • Energy can be measured in kilowatt-hours to make things easier.
  • Power is the rate of energy transferred.
  • Efficiency = useful energy/ total energy used.
  • Energy can be wasted as heat, sound or light depending on the system.