Energy - Section B - Six-mark questions

Six-mark questions are extended open response questions. These require longer answers than the structured questions with fewer marks. It is wise to plan your answer rather than rushing straight into it, otherwise you may stray away from the key points.

Six-mark questions are marked using a levels-based mark scheme because they are open ended. To gain full marks, you need to:

  • support explanations using scientific knowledge and understanding
  • use appropriate scientific words and terms
  • write clearly, linking ideas in a logical way
  • maintain a sustained line of reasoning, rather than getting lost or bogged down

You are likely to see command words such as:

  • 'describe' - you need to give an account but no reason
  • 'explain' - you must give reasons or explanations
  • 'devise' - you must plan or invent a procedure using your scientific knowledge and understanding
  • 'evaluate' - you must review information, including identifying strengths and weaknesses, and make a supported conclusion

Six-mark questions may be synoptic questions. These questions bring together ideas from two or more topics. For example, a question about atoms could include ideas about atomic structure, isotopes, radiation and nuclear reactions.

Remember that the topics covered in the first paper are assumed knowledge for the second paper, so questions in the second paper may need knowledge and understanding of those topics too.

The answers shown here give marking points as bullet points. You do not usually need to include all of them to gain six marks, but you do need to write in full sentences, linking them logically and clearly.

Sample question 1 - Foundation

Question

This question is about the kinetic energy of a rollercoaster car.

A graph shows the speed of a rollercoaster against the distance it has travelled along the track.

The graph shows how the speed of a 400 kg rollercoaster car changes as it goes along part of a rollercoaster track.

Describe how the kinetic energy of the car changes as it moves from A to D, and calculate the kinetic energy of the car at B. [6 marks]

OCR Gateway Science, GCE Physics, Paper B751, June 2015.

The kinetic energy of the car increases as the speed increases [1]. The speed increases between A and B, decreases between B and C and increases again between C and D [1]. The kinetic energy is greatest at B and zero at A. At B, the kinetic energy is greater than at D [1].

Calculation:

  • kinetic energy = 0.5 × mass × (speed)2 [1]
  • = 0.5 × 400 × 8 × 8 [1]
  • = 12,800 J [1]

Answering tip: Briefly plan the key points you want to include in your answer. For example:

  • say what happens to the speed and kinetic energy A-B, B-C and C-D
  • say when kinetic energy is greatest and lowest
  • calculate kinetic energy at point B (speed = 8 m/s, mass = 400 kg)

Sample question 2 - Higher

Question

This question is about kinetic and gravitational potential energy.

Look at the graph. It shows how the speed of a rollercoaster car changes with the distance travelled along part of the track.

The rollercoaster car starts from rest at the top of the track at A.

The car and its passengers have a total mass of 400 kg.

A graph shows the speed of a rollercoaster against the distance it has travelled along the track.

OCR Gateway Science, GCE Physics, Paper B751, June 2015 - Higher.

Kinetic energy increases from A to B and decreases from B to C [1]. The gravitational potential energy decreases from A to B and increases from B to C [1].

Calculation:

loss in gravitational potential energy = gain in kinetic energy [1]

kinetic energy = 0.5 × mass × (speed)2

maximum kinetic energy = 0.5 × 400 × 16 × 16 = 51,200 J [1]

gravitational potential energy = mass × height × g

51,200 = 400 × height × 10 [1]

height = 51,200 ÷ (400 × 10) = 12.8 m [1]

Answering tip: Briefly plan the key points you want to include in your answer. For example:

  • say what happens to the kinetic energy and gravitational potential energy A-B and B-C (not C-D)
  • calculate kinetic energy at point B (equal to gravitational potential energy)
  • calculate height from this