1. 1
   A roller coaster car of mass 500 kg descends through a vertical height of 20 m from the top of the first hill, where the gravitational field strength is 9.8 N/kg.

   (a)

   What is the loss in gravitational potential energy of the car?

   [1 mark]

   • A98000 J
   • B9800 J
   • C10000 J
   • D49 J

   (b)

   As the roller coaster car descends and speeds up, into which store is most of its gravitational potential energy transferred (ignoring energy losses to friction and air resistance)?

   [1 mark]

   • AThe chemical energy store
   • BThe kinetic energy store
   • CThe nuclear energy store
   • DThe electrostatic energy store

   (c)

   State the principle of conservation of energy, and use it to describe the energy transfer that takes place as the roller coaster car descends the hill, ignoring friction and air resistance.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A catapult is stretched back and then released, firing a stone of mass 0.05 kg, which leaves the catapult at a speed of 20 m/s.

   (a)

   What is the kinetic energy of the stone as it leaves the catapult?

   [1 mark]

   • A1 J
   • B20 J
   • C10 J
   • D500 J

   (b)

   In which energy store is the energy held while the catapult's elastic band is stretched, before it is released?

   [1 mark]

   • AThe internal (thermal) energy store
   • BThe kinetic energy store
   • CThe nuclear energy store
   • DThe elastic (strain) energy store

   (c)

   Describe the energy transfer that takes place from the moment the catapult is released to the moment the stone leaves it.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An electric kettle is switched on to boil some water. Separately, a car engine converts 100 J of chemical energy from its fuel, and tests show that this produces 25 J of useful kinetic energy, transfers 65 J to the internal (thermal) energy store of the surroundings via the engine block, and transfers 10 J to the surroundings by sound.

   (a)

   An electric kettle is switched on to boil some water. Describe the energy transfers that take place from the moment the kettle is switched on until the water reaches boiling point, naming the energy stores involved.

   [3 marks]

   (b)

   A car engine converts 100 J of chemical energy from its fuel during a short test. Measurements show that this produces 25 J of useful kinetic energy of the car, transfers 65 J to the internal (thermal) energy store of the surroundings via the hot engine block, and transfers 10 J to the surroundings as sound energy. Using the principle of conservation of energy, check whether these figures are consistent, and state which of these energy transfers is useful and which are wasted.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hydroelectric power station stores water at height behind a dam, releasing 100 J of energy for every unit of water that passes through, of which 85 J becomes useful electrical energy and 15 J is transferred to the internal energy store of the surroundings. Separately, a ball of mass 0.2 kg is thrown vertically upwards from the ground at a speed of 15 m/s.

   (a)

   A hydroelectric power station stores water at a height behind a dam. Describe the sequence of energy transfers that take place, from the stored water behind the dam to electrical energy delivered to homes, and describe how a Sankey-style diagram (described in words: for every 100 J of energy released from the stored water, 85 J becomes useful electrical energy and 15 J is transferred to the internal energy store of the surroundings) illustrates the conservation of energy in this process.

   [6 marks]

   (b)

   A ball of mass 0.2 kg is thrown vertically upwards from the ground at a speed of 15 m/s. Using the principle of conservation of energy and the equations for kinetic energy and gravitational potential energy, explain how the ball's kinetic energy and gravitational potential energy change as it rises, and calculate the maximum height reached by the ball, assuming air resistance is negligible.

   [6 marks]

   Total for question 4: 12 marks

End of questions