Work Done

• Work is done when an object is moved over a distance by a force applied in the direction of its displacement

  • It is said that the force does work on the object
  • If a force is applied to an object but doesn’t result in any movement, no work is done
• • When work is done on an object, energy is transferred
  • The amount of energy transferred (in joules) is equal to the work done (also in joules)

  energy transferred (J) = work done (J)
• Work is done when a force is used to move an object:

  
• Calculating Work Done,

  • The formula for work done is:

  Work done = force × distance
• Where:

  • W = work done in joules (J) or newton-metres (N m)
  • F =force in newtons (N)
  • s = distance/displacement in metres (m)
• Use the formula triangle to help you rearrange the equation:

  
• Examples of Work:

  • Work is done on a ball when it is lifted to a height 
  • The energy is transferred mechanically from the ball's kinetic energy store to its gravitational potential energy store
• The weight on the ball produced by the gravitational field does work on the ball over a distance :

  
• • Work is done when a bird flies through the air
  • The bird must travel against air resistance, therefore energy is transferred from the bird's kinetic store to its thermal store and dissipated to the thermal store of the surroundings
• Air resistance (drag) does work against the bird as it flies through the air: