Physics Topic 1

• Energy is always?


  Conserved.
• Energy cannot be?


  Created or destroyed.
• Energy is measured in?

  Joules (J).
• What are the different types of energy stores?

  Kinetic, Gravitational potential, Elastic potential, Thermal, Chemical, Nuclear, Magnetic and Electrostatic.
• How do we calculate Kinetic energy?

  1/2 x m x v^2

  • Kinetic energy measured in Joules
  • Mass measured in kg
  • Speed measured in m/s
• How do we calculate Gravitational Potential Energy?


  m x g x h

  • Mass is measured in kg
  • Gravitational field strength measured in 9.8N/Kg)
  • Height measured in m
• How do we calculate Elastic Potential Energy?


  1/2 x k x e^2

  • Elastic Potential Energy measured in Joules
  • Spring constant in N/m (k)
  • Extension in m (e)
• How do we calculate Thermal Energy?


  m x c x change in temperature

  • Mass measured in kg
  • Specific heat capacity is the energy needed to raise the temp of 1kg of a substance by 1 Celsius and is measured in J/kg per Celsius
  • Change in temp measured in Celsius
• What happens in a open system?


  Both energy & matter are exchanged with its surroundings.
• What happens in a closed system?

  No exchange of matter with surroundings.
• What is power and how is it calculated?

  Power is the rate of energy transfer.

  P = E/t

  • Power is measured in watts
  • Energy transferred is measured in joules
  • Time is measured in seconds
• What is efficiency and how is it calculated?

  Efficiency is the ratio of total input energy/power that is converted to useful output energy.

  Efficiency = Useful E or P out/total E or P in

  (x100) - to turn from a decimal to percentage
• How is thermal energy lost and how can it be prevented?

  Through conduction which transfers energy to outside surroundings.

  Insulation e.g. Cavity walls, double glazing etc reduces this
• What are finite/non-renewable energy resources?

  Fossil Fuels e.g. coal,oil & natural gases burnt to produce heat that produces steam to drive turbines and generators.

  Nuclear fuel e.g. uranium used in nuclear reactors produces heat
• What are renewable energy sources?

  • Wind power uses kinetic energy to turn turbines used to power a generator to produce energy
  • Hydroelectric uses water behind dam that has GPE which falls through turbine
  • Solar power uses light from sun to produce electricity
  • Biofuels burn plant matter to produce heat