Gravity and Gravitational Fields
Gravity and Gravitational Fields
- Any two masses pull each other. This pull is called .
- The Earth pulls you, a falling object and the Moon towards its centre.
Gravitational force between masses
- Gravitational force is not only a force on a falling object. Your weight is the gravitational force from the Earth on you.
- The masses do not need to touch. The Earth and the Moon are far apart, but each one pulls the other.
- Gravitational force always pulls masses together. It never pushes them apart.
- Each red arrow starts at the mass that feels the force. Each arrow points towards the centre of the Earth.
- The Earth pulls the same mass near the Earth and far from the Earth. The pull becomes weaker when the distance becomes larger.
From force to field
- A force tells us how one mass is being pulled. A field tells us where another mass would feel a pull.
- A is the part of space where a mass feels a gravitational force. This is the simple meaning of a field.
- The field exists before a second mass is placed there. A small shows the force at one point.
- The force on each kilogram is called , . A later lesson calculates it.
Definition
1 markWhat is meant by gravitational field at a point?
Model answer: The gravitational force per unit mass at that point (9702/41/O/N/25 Q3(a)).
Common mistake
The word field can mean the whole region. The words at a point ask for the field strength at one position. Write force per unit mass.