1. 1
   A warehouse worker pushes a wooden crate a distance of 8 m across a horizontal floor by applying a constant horizontal force of 45 N. The crate moves at a slow, constant speed throughout.

   (a)

   Which equation is used to calculate the work done by the worker on the crate?

   [1 mark]

   • AE = F × d
   • BE = m × g × h
   • CP = E ÷ t
   • DE = ½ × m × v²

   (b)

   What is the correct SI unit for the work done by the worker on the crate?

   [1 mark]

   • Awatt (W)
   • Bjoule (J)
   • Cnewton (N)
   • Dnewton per metre (N/m)

   (c)

   Calculate the work done by the worker as the crate moves the full 8 m distance. Show your working and give the correct unit.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student lifts a ball of mass 2 kg from the ground to a height of 5 m above the ground, then releases it so that it falls freely towards the ground. Take the gravitational field strength, g, as 10 N/kg.

   (a)

   As the ball falls freely after being released, what happens to its gravitational potential energy (GPE) and its kinetic energy (KE)?

   [1 mark]

   • ABoth GPE and KE stay the same
   • BGPE increases and KE decreases
   • CBoth GPE and KE decrease
   • DGPE decreases and KE increases

   (b)

   Which equation would be used to calculate the gravitational potential energy gained by the ball when it was lifted to a height of 5 m?

   [1 mark]

   • AGPE = ½ × m × v²
   • BGPE = F × d
   • CGPE = m × g × h
   • DGPE = E ÷ t

   (c)

   Calculate the GPE gained by the ball when it was lifted to a height of 5 m. Use your answer, and the idea that energy is conserved as the ball falls, to state the KE of the ball just before it hits the ground.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An electric motor is used to lift a load of mass 15 kg vertically through a height of 4 m in a time of 6 s. The motor is supplied with 1500 J of electrical energy during this lift. Take g = 10 N/kg.

   (a)

   Calculate the useful energy transferred to the load as it is lifted, and use this to calculate the power output of the motor.

   [3 marks]

   (b)

   Calculate the efficiency of the motor as a percentage. State one reason why the efficiency of the motor is less than 100%.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A cyclist and their bicycle have a combined mass of 80 kg. Starting from rest at the top of a hill, the cyclist free-wheels (does not pedal or brake) down the hill, which has a vertical height of 20 m. Because of air resistance and friction in the wheel bearings, the cyclist reaches the bottom of the hill travelling at 15 m/s, which is slower than would be predicted from the GPE lost alone. Take g = 10 N/kg.

   (a)

   Using ideas about energy transfers, explain what happens to the energy of the cyclist–bicycle system as it travels down the hill. Calculate the GPE lost, the KE gained, and the amount of energy dissipated by resistive forces by the time the cyclist reaches the bottom of the hill.

   [6 marks]

   (b)

   The cyclist wants to reduce the amount of energy dissipated by resistive forces on this descent, so that a greater proportion of the GPE lost is transferred to useful KE at the bottom of the hill. Suggest three practical changes the cyclist could make to their bicycle or riding position, and for each one explain, using physics ideas, why it would reduce the energy dissipated.

   [6 marks]

   Total for question 4: 12 marks

End of questions