Maintaining Circular Motion
- An object moving in a circle is not in equilibrium, it is constantly changing direction
- Therefore, in order to produce circular motion, an object requires a resultant force to act on it
- This resultant force is known as the centripetal force and is what keeps an object moving in a circle
- The centripetal force F is defined as:
The resultant force towards the centre of the circle required to keep a body in uniform circular motion. It is always directed towards the centre of the body's rotation.
The tension in the string provides the centripetal force F to keep the hammer in circular orbit
- Note: centripetal force and centripetal acceleration act in the same direction
- This is due to Newton’s Second Law
- The centripetal force is not a separate force of its own
- It can be any type of force, depending on the situation, which keeps an object moving in a circular path
Examples of centripetal force
Examiner Tip
Make sure you are able to give examples of centripetal forces, understanding that many types of familiar forces (e.g., gravity, electric) can act as centripetal forces.
A classic example that often comes up in your magnetic fields topic is the magnetic force on a charged particle, which is always centripetal. This is because the force acts at 90° to the charged particle's velocity, causing it to move in a circle.
