1. 1
   A large pendulum clock is displayed in a science museum. Visitors watch a heavy brass bob swing on the end of a rigid rod from one side to the other and back again, over and over.

   (a)

   At the highest point of its swing, which energy store of the pendulum bob is at a maximum?

   [1 mark]

   • AKinetic energy store
   • BGravitational potential energy store
   • CElastic potential energy store
   • DChemical energy store

   (b)

   As the bob swings from its highest point down to the lowest point of its swing, energy is transferred mainly from which store to which store?

   [1 mark]

   • AChemical to thermal
   • BKinetic to elastic potential
   • CGravitational potential to kinetic
   • DElastic potential to chemical

   (c)

   The museum guide tells visitors that, without a small motor to keep it going, the pendulum would gradually swing through a smaller and smaller distance each time until it stopped completely. Explain, in terms of energy stores, why this happens.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In a packaging factory, an electric motor drives a conveyor belt that lifts boxes of goods from ground level up to a loading platform. The motor is supplied with 500 J of electrical energy for every box lifted, but only 350 J is usefully transferred to the gravitational potential energy store of each box.

   (a)

   Which of the following best describes the 350 J transferred to a box's gravitational potential energy store?

   [1 mark]

   • AWasted energy
   • BEnergy stored chemically
   • CTotal energy input
   • DUseful energy output

   (b)

   The remaining 150 J is mostly dissipated to the thermal energy store of the surroundings. This dissipation happens mainly because of...

   [1 mark]

   • AFriction between the moving parts of the motor and belt
   • BAn increase in the gravitational potential energy of the conveyor belt itself
   • CA loss of chemical energy from the boxes
   • DThe motor storing elastic potential energy

   (c)

   Calculate the efficiency of the conveyor belt system. Give your answer as a percentage.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A hydroelectric power station stores water in a reservoir high above a valley. When electricity demand is high, gates are opened and water flows down through pipes to turbines far below, generating electricity. Engineers calculate that for every 1000 J of gravitational potential energy stored in the water at the top, only 800 J is usefully transferred to the electrical energy store by the generators.

   (a)

   Describe the energy transfers that take place, in order, from the water at the top of the reservoir to the electricity generated by the turbines.

   [3 marks]

   (b)

   Calculate the efficiency of this energy transfer, and suggest one reason why the efficiency is less than 100%.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A vintage steam locomotive on display at a railway heritage centre once burned coal to heat water into steam, which drove pistons to turn the wheels. Engineers of the time knew that only a fraction of the chemical energy stored in the coal ended up as useful kinetic energy of the moving train; the rest was dissipated to the surroundings, mainly as heat from the boiler and funnel, and as sound.

   (a)

   Using ideas about energy stores and dissipation, explain what happens to the chemical energy stored in the coal as the locomotive moves, and explain how a Sankey diagram could be used to represent these energy transfers.

   [6 marks]

   (b)

   The heritage centre wants to build a smaller working replica that is more energy efficient than the original. Discuss two design features that could be included, and explain how each would reduce the amount of energy dissipated.

   [6 marks]

   Total for question 4: 12 marks

End of questions