Work Done (OCR Gateway GCSE Physics: Combined Science)

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)
• You can rearrange this equation with the help of the formula triangle:

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