5.2

• If a force is said to do 'work', it means the force causes an object to be displaced through a distance
• The equation used to calculate work done is: Work done = Force x Distance. The appropriate units are: Work done (Joules), Force (Newtons), Distance (metres)
• The distance that must be used when calculating work done is the distance that is moved along the line of action of the force
• 1 joule of work is done when a force of 1 Newton causes a displacement of 1 metre
• 1 joule of energy is equal to 1 Newton metre (1 Nm = 1 J)
• The work done by a force acting on an object over a distance of 5m with a force of 10N is 50 Joules (10 x 5 = 50 Nm = 50 J)
• When work is done against frictional forces:

  • A rise in temperature of the object occurs
  • Kinetic energy is converted to heat
• Air resistance slows down a projectile because:

  • The object does work against the air resistance
  • Kinetic energy is converted into heat, slowing down the object