power and work done

• How many definitions of power are there?

  Two definitions
• What is the first definition of power?

  Rate at which energy is transferred
• What is the equation for power based on energy transferred?

  Power = energy transferred / time
• What is the second definition of power?

  Rate at which work is done
• What is the equation for power based on work done?

  Power = work done / time
• What does "work done" refer to?

  Energy transferred using a force
• If you push a car down the road, what is the energy referred to as?

  Work done
• How is power measured?

  In watts
• How are energy transferred and work done measured?

  In joules
• How is time measured in these equations?

  In seconds
• How do you calculate power using energy transferred?

  • Power = energy transferred / time
  • Example: 1200 joules over 20 seconds
  • Calculation: 1200 / 20 = 60 watts
• How do you calculate power using work done?

  • Power = work done / time
  • Example: 9 kilojoules over 20 seconds
  • Calculation: 9000 / 20 = 450 watts
• What is the power of a lamp that transfers 1200 joules over 20 seconds?

  60 watts
• What is the power of a lamp that transfers 1500 joules over 30 seconds?

  50 watts
• Which lamp is more powerful if one transfers 1200 joules over 20 seconds and the other 1500 joules over 30 seconds?

  The left lamp is more powerful
• How do you convert 3 minutes into seconds?

  180 seconds
• If an 1100 watt microwave runs for 3 minutes, how much energy is transferred?

  198,000 joules
• How do you convert 198,000 joules to kilojoules?

  198 kilojoules
• How much work is done if you push a car with 9 kilojoules over 20 seconds?

  450 watts
• What is the final power calculated for pushing a car with 9 kilojoules over 20 seconds?

  450 watts
• What are the key units of measurement in power calculations?

  • Power: watts
  • Energy transferred: joules
  • Work done: joules
  • Time: seconds