Explain how the concept of a field is used to describe the interaction between two masses separated by empty space, and describe what happens to the field strength as the distance between the masses increases.

AQA A-Level Physics (7408) — 3.7.1 Fields · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

A field is a region of space where a force is experienced by an appropriate object.
A gravitational field exists around any object with mass.
The field allows us to describe the force on one mass without the masses physically touching, explaining action at a distance.
As the distance between the masses increases, the gravitational field strength decreases.
Field lines spread further apart or become less dense at greater distances, showing the field is weaker.

Examiner tips

  • Use the term ‘field’ and ‘gravitational field’ early. Show the inverse‑square relationship by mentioning field lines becoming less dense. Keep the answer concise, matching the 5 marks.

Mark scheme (5 marks)

  1. A field is a region of space where a force is experienced (by an appropriate object)
  2. A gravitational field exists around any object with mass
  3. The field allows us to describe the force on one mass (or object) without the masses physically touching / explains action at a distance
  4. As the distance between the masses increases, the gravitational field strength decreases
  5. Field lines spread further apart / become less dense at greater distances, showing the field is weaker

Key terms in this question

field · field strength

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