power

• Energy


  A key principle in physics, as it allows work to be done
• Power


  The rate at which energy is transferred
• Efficiency


  The amount of energy that is usefully transferred
• Work


  The measure of energy transfer when a force (F) moves an object through a distance (d)
• Energy transferred = work done
• Energy transferred and work done are both measured in joules (J)
• Calculating work done


  1. Depends on the size of the force acting on the object

  2. The distance through which the force causes the body to move in the direction of the force
• Work done (W)


  Measured in joules (J)
• Force (F)


  Measured in newtons (N)
• Distance (d)


  Measured in metres (m)
• One joule of work is done (or one joule of energy is transferred) when a force of one newton causes a body to move through a distance of one metre
• Calculating work done


  • Force of 10 N causes a box to move a horizontal distance of 2 m, so work done = 10 x 2 = 20 J
• Calculating work done


  • Horizontal force of 50 N causes a trolley to move a horizontal distance of 30 m, so work done = 50 x 30 = 1,500 J
• Calculating force


  • 12,000 J of energy is supplied to move a small truck a distance of 80 m, so force = 12,000 / 80 = 150 N