Work & power

• Power


  The rate at which energy is transferred
• Power


  The rate at which work is done
• Calculating power (energy transfer)

  Energy transferred / Time taken
• Calculating power (work done)


  Work done / Time taken
• Work done is a special measure of energy transferred when a force is used to move an object by a certain distance
• Energy transferred and work done are measured in joules, time is measured in seconds, and power is measured in watts
• Calculating energy transferred for a 1100 watt microwave on for 3 minutes


  Power x Time

  1100 watts x 180 seconds

  198,000 joules or 198 kilojoules
• Calculating power when 9 kilojoules of work is done over 20 seconds


  Work done / Time taken

  9,000 joules / 20 seconds

  450 watts
• The unit of power is watts (W)
• Speed can be calculated using the formula v=d/t where v is average speed, d is displacement, and t is time.
• Average speed = total distance travelled / total time taken
• Average Velocity = Distance Travelled / Time Taken