Work done and energy transfers

• What does it mean if a force is said to do ‘work’?

  The force causes an object to be displaced through a distance
• what is the equation used to calculate work done? Units?

  work done = force x distance

  • work done in joules (j), force in newtons (N), distance in metres (m)
• what distance must be used when calculating work done?

  it must be the distance that is moved along the line of action of the force.
• under what circumstance is 1 joule of work done?

  when a force of 1 newton causes a displacement of 1 metre
• how many newton-metres are equal to 1 joule of energy?

  1Nm = 1J
• how much work is done by the force acting on the below object over a distance of 5m?

  10 x 5 = 50Nm = 50J

  
• what occurs when work is done against frictional forces?

  • a rise in temperature of the object occurs
  • kinetic energy is converted to heat
• why does air resistance slow down a projectile?

  • the object does work against the air resistance
  • kinetic energy is converted in to heat, slowing down the object