Point Mass Approximation
- For a point outside a uniform sphere, the mass of the sphere may be considered to be a point mass at its centre
- A uniform sphere is one where its mass is distributed evenly
- The gravitational field lines around a uniform sphere are therefore identical to those around a point mass
- An object can be regarded as point mass when:
A body covers a very large distance as compared to its size, so, to study its motion, its size or dimensions can be neglected
- An example of this is field lines around planets
Gravitational Field Lines Around a Planet
Gravitational field lines around a uniform sphere are identical to those on a point mass
- Radial fields are considered non-uniform fields
- So, the gravitational field strength g is different depending on how far you are from the centre of mass of the sphere
