# Gravitational Fields

AQA A - Gravitational Fields

- Created by: Amy
- Created on: 03-01-13 12:58

First 173 words of the document:

PHY4A

Gravitational Fields

A gravitational field exists around any mass, no matter how large or small. Other masses in this region

will feel a force, which is always attractive: a repulsive gravitational force has never been identified.

Gravitational field lines

Gravitational fields are always drawn using gravitational field lines, which show the direction of the

force on a mass placed at any point in the field. Around a spherical mass the lines look like this:

Near the Earth's surface, the field is nearly uniform and the lines are evenly spaced:

Gravitational field strength, g

The gravitational field strength g at a point in a field is the force per unit mass on an object placed at

that point:

F

g = m

It follows from Newton's universal law of gravitation that, around a spherical mass M:

g = GM

r²

Where r is the distance from the centre of the mass.

Note that:

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