Work Done | Physics for GCSE/IGCSE - Year 11 PDF Download

Work Done & Energy Transfers

• Work is done when a force is used to move an object over a distance.
• When a force is applied in the direction of an object's displacement, work is said to be done as the force acts on the object.
• If a force is exerted on an object but it does not lead to any movement, no work is considered to be done.

• The concept of work done is expressed by the formula: 
• In this formula:
  • W represents work done in joules (J) or newton-metres (N m)
  • F stands for force in newtons (N)
  • d denotes the distance in meters (m)
• You can rearrange this equation using a formula triangle for better understanding.
  
• Multiplying force by distance yields units of newton-metres (N m), with work measured in joules (J).
• This relationship leads to a straightforward conversion: 1 J = 1 N m, where one joule equals the work done by a force of one newton acting through one meter.
• Consequently, conversions between joules and newton-metres are uncomplicated, as the number of joules equates to the number of newton-metres.
• Whenever mechanical work is executed, energy is mechanically transferred from one store to another, with the amount of energy transferred (in joules) equating to the work done (in joules or newton-metres).
• If a force aligns with the direction of an object's movement, the object gains energy, typically to its kinetic energy store. Conversely, if the force opposes the movement, the object loses energy, often dissipated to the surroundings, usually as heat.
• Therefore, the equation can be summarized as: W = Fd = ΔE.

Examples of Work

• When work is done on a ball by lifting it, energy is transferred from the ball's kinetic energy store to its gravitational potential energy store.
• The weight of the ball, due to gravity, performs work on the ball over a distance.

Work Done by a Bird Flying Through the Air

• The bird expends energy to travel against air resistance.
• This results in the transfer of energy from the bird's kinetic store to its thermal store.
• The dissipated energy is released to the thermal store of the surroundings.