work done by a force

• What is the definition of work done?

  Work is done whenever energy is transferred from one store to another
• What are the two different cases of work done mentioned?

  • Mechanical work: using a force to move an object
  • Electrical work: a current transferring energy
• In the example of the dog pulling a sledge, what type of energy is transferred from the dog to the sledge?

  The chemical energy store in the dog is transferred to the kinetic energy store in the moving sledge
• What happens to some of the kinetic energy of the sledge due to friction?

  Some of the kinetic energy is transferred to the thermal energy store in the sledge runners and the ground
• What is the force applied by the dog in the example?

  50 Newtons
• What distance does the sledge move in the example?

  3 meters
• How do you calculate work done?

  Work done in joules equals the force in Newtons multiplied by the distance in meters
• What is the equation for calculating work done?

  Work done (J) = Force (N) × Distance (m)
• What is the total work done when a force of 50 Newtons moves a sledge 3 meters?

  150 joules
• What does the work done of 150 joules indicate in the example?

  It indicates that 150 joules of energy was transferred from the chemical energy store in the dog to the kinetic and thermal energy stores
• What happens to the kinetic energy store of a car when the driver applies the brakes?

  The kinetic energy store is transferred to the thermal energy store in the brakes
• What is the speed of the car before the brakes are applied?

  20 m/s
• If a force of 2,000 Newtons is applied to the brakes of a car that takes 20 meters to stop, how do you calculate the work done?

  Work done equals the force multiplied by the distance
• What is the work done when a force of 2,000 Newtons is applied over a distance of 20 meters?

  40,000 joules
• What does the work done of 40,000 joules indicate in the braking example?

  It indicates that 40,000 joules of kinetic energy was transferred to the thermal energy store in the brakes
• What should you be able to do by the end of the video regarding work done?

  • Describe what's meant by work done
  • Calculate work done by a force acting on an object