Gravitational Field Strength
Physics: AQA A Level, topic 7.2.2
Gravitational Field Lines
The gravitational field lines around a point mass or spherical mass are radial.
Point mass
- The diagram shows the gravitational field lines around a point mass.
- The field lines are all pointing towards the mass because gravitational forces are attractive.
- The lines indicate the direction of the gravitational force on another point mass, placed near to first.
Spherical mass
- The diagram shows the gravitational field lines around a spherical planet.
- All of the field lines seem to be pointing towards the centre of the planet.
Close to the surface of Earth
- Close to the surface of the planet and over a small distance, the field lines seem to be equally spaced and parallel.
- This is why, in our everyday experience, we think that the Earth’s gravitational field is uniform.
Gravitational Field Strength
Gravitational field strength, g, is the same as the acceleration due to gravity.
Field strength
- Gravitational field strength, g , is defined by the relationship:
- Where F is the gravitational force on the object and m is the mass of the object.
Test yourself on Gravitational Field Strength
Which of these is NOT a definition of g?