1. 1
   A lift motor does 60000 J of work raising a lift full of passengers in 12 s.

   (a)

   What is the power output of the motor?

   [1 mark]

   • A5000 W
   • B720000 W
   • C60012 W
   • D0.0002 W

   (b)

   In which unit is the power output of the lift motor measured?

   [1 mark]

   • AThe joule
   • BThe watt
   • CThe newton
   • DThe second

   (c)

   A second, more powerful lift motor does the same 60000 J of work raising an identical lift, but in only 8 s. Explain what it means for this motor to be 'more powerful', and calculate its power output.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An electric water pump transfers 45000 J of energy to pump water from a well in 30 s. A second, older pump transfers the same 45000 J of energy in 45 s.

   (a)

   What is the power output of the pump?

   [1 mark]

   • A45030 W
   • B1350000 W
   • C1500 W
   • D0.00067 W

   (b)

   A second, older pump transfers the same 45000 J of energy pumping the same amount of water, but takes 45 s to do so. Which pump has the greater power output?

   [1 mark]

   • AIt cannot be determined from the information given
   • BThe second pump, which took 45 s
   • CBoth pumps have exactly the same power output
   • DThe first pump, which took 30 s

   (c)

   State the equation linking power, energy transferred and time, and use it to calculate the power output of the second (older) pump.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A tower crane lifts a load, doing 240000 J of work in 20 s. A smaller, second crane performs the identical lift (240000 J of work) but takes 32 s to do so.

   (a)

   Calculate the power output of the crane during this lift.

   [3 marks]

   (b)

   A smaller, second crane performs the identical lift (240000 J of work), but takes 32 s to do so. Calculate the power output of the second crane, and explain what this comparison shows about the two cranes.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A physics class investigates power output, comparing a student's power running up a flight of stairs with an electric motor rated at 2000 W used to lift the same weight through the same height.

   (a)

   Describe an experiment to determine a student's power output when running up a flight of stairs, stating the measurements that would need to be taken and explaining how the results would be used to calculate power, including a sample calculation for a student of weight 600 N who rises a vertical height of 3.0 m in 2.5 s.

   [6 marks]

   (b)

   An electric motor rated at 2000 W is used to lift the same 600 N weight through the same 3.0 m height as the student in the previous question. Calculate the time this motor would take to lift the weight, compare this with the student's performance, and explain what it means physically for the motor to have a higher power rating than the student.

   [6 marks]

   Total for question 4: 12 marks

End of questions