1. 1
   Two removal workers each carry an identical wardrobe of weight 800 N up a flight of stairs of height 4 m. Worker A takes 20 s to climb the stairs and Worker B takes 30 s.

   (a)

   Two removal workers each carry an identical wardrobe up a flight of stairs of the same height. Worker A takes 20 s and Worker B takes 30 s. Which statement about the two workers is correct?

   [1 mark]

   • AWorker A does more work than Worker B
   • BWorker A has a greater power output than Worker B
   • CWorker B has a greater power output than Worker A
   • DWorker A and Worker B transfer the same amount of energy at the same rate

   (b)

   Which equation correctly links power, work done and time?

   [1 mark]

   • AP = W x t
   • BP = W + t
   • CP = t / W
   • DP = W / t

   (c)

   Calculate the power output of Worker A while carrying the wardrobe up the stairs. Show the equation used, your working, and give the final answer with unit.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A tug boat pulls a barge along a canal using a horizontal rope with a tension force of 12000 N. The barge moves 50 m along the line of the rope's pull, taking 100 s.

   (a)

   What quantity does the product of the force and the distance moved represent?

   [1 mark]

   • AThe power delivered by the tug boat
   • BThe momentum of the barge
   • CThe work done by the tug boat on the barge
   • DThe elastic potential energy of the rope

   (b)

   Which unit is equivalent to one joule?

   [1 mark]

   • AOne newton-metre
   • BOne newton per metre
   • COne newton per second
   • DOne watt per second

   (c)

   Calculate the power delivered by the tug boat's rope as it pulls the barge along the canal. Show the equation used, your working, and give the final answer with unit.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hospital lift motor can raise a fully loaded lift car of weight 15000 N through a height of 12 m in 15 s. The hospital wants to install a faster motor to raise the same lift car through the same height in only 9 s.

   (a)

   Calculate the useful power output of the lift motor, giving your answer to an appropriate number of significant figures.

   [3 marks]

   (b)

   The hospital wants to install a faster lift motor so that the same lift car can be raised through the same height of 12 m in only 9 s instead of 15 s. Explain what must be true about the new motor's power output compared with the original motor, and calculate the minimum power output required for the new motor.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Two competing manufacturers advertise electric bicycle motors: Motor X (250 W) and Motor Y (400 W). A cyclist and bicycle of total mass 90 kg want to climb a hill that rises 20 m vertically, using one of these motors.

   (a)

   Explain what is meant by power in this context, and use the concept of power to explain and calculate how long each motor would take to lift the cyclist and bicycle up the hill, assuming all the motor's power is usefully transferred to gravitational potential energy store of the cyclist and no energy is transferred to the thermal energy store.

   [6 marks]

   (b)

   In reality, not all of the electrical energy supplied to an electric bicycle motor is transferred usefully to the gravitational potential energy store of the cyclist when climbing a hill. Evaluate the factors that would cause the actual time taken to climb the hill to be longer than the calculated times for Motor X and Motor Y, and discuss how a manufacturer could design a motor system to reduce these losses.

   [6 marks]

   Total for question 4: 12 marks

End of questions