Topic 8-Energy and Forces doing Work

• What is the principle of energy conservation?

  Energy is never created or destroyed
• What happens to energy when a system changes?

  Energy is transferred from one form to another
• How does electrical energy change in a motor?

  It changes into kinetic energy
• What is a closed system?

  A system with no external forces
• What remains the same in a closed system?

  The total energy remains the same
• What is the formula for change in gravitational potential energy?

  ∆GPE = mg∆h
• What does each variable in ∆GPE = mg∆h represent?

  m = mass, g = gravitational field strength, ∆h = height change
• What is the formula for kinetic energy?

  KE = ½ mv²
• What does each variable in KE = ½ mv² represent?

  m = mass, v = speed
• What is work done in physics?

  Energy transferred by an external force
• What is the formula for work done?

  W = Fd
• What do the variables in W = Fd represent?

  F = force, d = distance moved
• Why is energy rarely 100% transferred into the desired form?

  Some energy is dissipated as waste
• What causes energy dissipation in mechanical processes?

  Friction causing heat generation
• What is power in physics?

  The rate at which energy is transferred
• What is the formula for power?

  P = E/t
• What do the variables in P = E/t represent?

  E = energy transferred, t = time taken
• What is the definition of efficiency?

  Measure of energy not lost as waste
• How is efficiency calculated?

  Efficiency = useful output energy / total input energy
• What is the unit of power?

  Watt (W)
• What is the unit of energy?

  Joule (J)
• What is the unit of work done?

  Joule (J)
• What is the unit of efficiency?

  It is a ratio, no unit
• What happens to energy in a heating process?

  Electric energy transfers to thermal energy
• What are the forms of energy transfer in different processes?

  • Electrical energy to kinetic energy in motors
  • Chemical potential energy to electric energy in batteries
  • Electric energy to thermal energy in heating
• What are the key concepts related to energy in physics?

  • Energy conservation: never created or destroyed
  • Closed systems: total energy remains constant
  • Work done: energy transferred by external forces
  • Power: rate of energy transfer
  • Efficiency: measure of energy not lost as waste