Gravitational field
● VERBATIM — examined word-for-wordA gravitational field is a region of space in which a mass experiences a gravitational force. It is an example of a field of force.
What this actually means
This is the cheapest definition mark in the topic and the one most people fumble, because it sounds too obvious to be worth learning. Say region of space, say a mass, say experiences a force. Three ideas, one line.
The word field exists so we can talk about what the Earth does to space itself, without having to name the second object. Earth sets up the field everywhere; the field only shows itself when you put a mass in it. That is why the definition is phrased as a conditional: a mass placed there WOULD experience a force.
Syllabus LO (a) also wants you to know this is an example of a field of force, i.e. the same idea as an electric field or a magnetic field. Examiners sometimes ask you to name another field of force, so keep electric field in your back pocket.
Do not write 'a region where gravity acts' or 'a region around a mass'. Neither names the test object or the force, so neither scores. The field extends to infinity in principle, it just becomes negligibly weak, so avoid saying it 'stops' anywhere.
Defining the field without mentioning that a mass placed there experiences a force.
Prove it — watch it be true
- Load the Earth planet preset and look at the 3D field vector arrows filling the space around the planet.
- Drag the test mass probe to any empty point and read the non-zero F and g readouts, showing a mass placed there does feel a force.
- Drag the probe far out and watch the arrows shrink but never vanish, so the field has no edge.