# Maintaining Circular Motion(Edexcel International A Level Physics)

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Katie M

Expertise

Physics

## 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

#### Exam 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.

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