Centripetal Force (Oxford AQA IGCSE Physics)

A less massive body or object will orbit a more massive body or object

• For example:

  • A planet orbiting a Sun

  • A satellite orbiting the Earth

For any object to be in orbit, there must be a force pulling the object toward the centre of the orbit

This force is called the centripetal force

• For an object in space, the centripetal force is gravity

The gravitational force exerted by the more massive body on the orbiting object is always attractive

• Therefore, the gravitational force always acts towards the centre of the larger body

The gravitational force will cause the body to move in a circular path

So the gravitational force acts at right angles to the direction of motion

The force of gravity always acts towards the centre of the orbit

This is an unbalanced force and therefore causes acceleration towards the centre of the orbit

• Constantly changing the direction of motion of the body and therefore its velocity

Velocity is a vector quantity

• Equal to speed in a given direction

The speed of the object moving in a circle is constant because it is travelling the same distance every second

• This means that an object moving in circular motion travels at a constant speed but has a changing velocity

An object that has a constantly changing velocity therefore has acceleration