Work Done by Force

• What is meant by work done?

  Work done is the transfer of energy from one store to another.
• What are the two different cases of work done discussed?

  • Mechanical work: using a force to move an object
  • Electrical work: current transferring energy
• How is mechanical work defined?

  Mechanical work involves using a force to move an object.
• What happens to energy when a dog pulls a sledge?

  The chemical energy in the dog is transferred to the kinetic energy of the sledge.
• What energy transfers occur when a dog pulls a sledge?

  • Chemical energy in the dog to kinetic energy in the sledge
  • Kinetic energy in the sledge to thermal energy in the sledge runners and ground due to friction
• What is the equation to calculate work done?

  Work done (in Joules) = Force (in Newtons) × Distance (in meters)
• If a force of 50 Newtons moves an object 3 meters, how much work is done?

  150 Joules
• What happens to the kinetic energy of a car when it brakes?

  The kinetic energy is transferred to the thermal energy store in the brakes.
• What is the process of energy transfer when a car brakes?

  1. Kinetic energy of the moving car
  2. Friction between brakes and wheels
  3. Transfer of kinetic energy to thermal energy in the brakes
  4. Increase in brake temperature and car slowing down
• If a force of 2000 Newtons is applied to a car that travels 20 meters to stop, how much work is done?

  40,000 Joules
• What is the total work done when a dog pulls a sledge with a force of 50 Newtons over a distance of 3 meters?

  150 Joules
• What is the total work done when a car brakes with a force of 2000 Newtons over a distance of 20 meters?

  40,000 Joules