Energy - forces doing work

• What is the principle regarding the creation and destruction of energy?

  Energy is never created or destroyed; it is only transferred.
• What happens to energy when a system changes?

  Energy is transferred from one form to another.
• In a motor, what type of energy changes into kinetic energy?

  Electrical energy changes into kinetic energy.
• What is a closed system?

  A closed system is one that experiences no external forces.
• Give an example of a closed system.

  A circuit or a skydiver can be examples of a closed system.
• What remains the same in a closed system at all times?

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

  ∆GPE = mgh
• What does the variable 'm' represent in the gravitational potential energy formula?

  'm' represents mass in kilograms (kg).
• What does 'g' represent in the gravitational potential energy formula?

  'g' represents gravitational field strength in newtons per kilogram (N/kg).
• What does '∆h' represent in the gravitational potential energy formula?

  '∆h' represents the change in vertical height in meters (m).
• What is the formula for kinetic energy?

  KE = \frac{1}{2} mv^2
• What does the variable 'v' represent in the kinetic energy formula?

  'v' represents speed in meters per second (m/s).
• What is work done in terms of energy transfer?

  Work done is when an external force transfers energy to a system.
• Give an example of work done.

  A human doing work to push a ball up a hill is an example of work done.
• What type of energy is formed from chemical potential energy in batteries?

  Chemical potential energy forms electric energy.
• How does electric energy transfer to thermal energy?

  Electric energy transfers to thermal energy as work is done against the heating coils.
• What is the formula for work done?

  Work done = Fd
• What does 'F' represent in the work done formula?

  'F' represents force in newtons (N).
• What does 'd' represent in the work done formula?

  'd' represents distance moved in the direction of the force in meters (m).
• Why is energy rarely 100% transferred into the desired form?

  Some energy is dissipated and stored in less useful ways.
• What makes mechanical processes wasteful?

  Mechanical processes are wasteful when they get hot, usually due to friction.
• What happens to energy when it is dissipated as heat?

  Energy is lost to the surroundings when dissipated as heat.
• What is power in terms of energy transfer?

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

  Power = \frac{E}{t}
• What does 'E' represent in the power formula?

  'E' represents energy transferred or work done in joules (J).
• What does 't' represent in the power formula?

  't' represents time taken in seconds (s).
• How many watts are in one joule per second?

  1 Watt is equal to 1 Joule per second.
• What does efficiency measure?

  Efficiency measures how much energy is not lost as waste.
• What is the formula for efficiency?

  Efficiency = \frac{\text{useful output energy}}{\text{total input energy}}
• What are the key concepts related to energy transfer?

  • Energy is never created or destroyed, only transferred.
  • Energy changes form during system changes.
  • Work done transfers energy to a system.
  • Energy is rarely 100% transferred; some is dissipated as waste.
  • Power is the rate of energy transfer.
  • Efficiency measures energy not lost as waste.
• What is a closed system in physics?

  A closed system experiences no net change in its total energy when energy transfers occur within it.
• What does the dissipation of energy refer to?

  Dissipation of energy refers to energy that is transferred to and spread out in the surroundings, usually in the form of heat.
• What is the definition of efficiency in energy transfer?

  Efficiency is the ratio of useful output energy transfer to total energy input.
• Why can efficiency never exceed 1 or 100%?

  Efficiency can never exceed 1 (or 100%) due to the conservation of energy.
• What is gravitational potential energy?

  Gravitational potential energy is the store of energy that all raised matter has.
• What factors affect gravitational potential energy?

  Gravitational potential energy is directly proportional to the mass of the object, the distance it is raised, and the gravitational field strength at that point.
• What is kinetic energy?

  Kinetic energy is the store of energy that all moving matter has.
• How is kinetic energy related to mass and velocity?

  Kinetic energy is directly proportional to the object's mass and to the square of its velocity.
• What is power in the context of energy transfer?

  Power is the rate at which energy is transferred or the rate at which work is done.
• How is power calculated?

  Power is calculated by dividing the work done by the time taken.