What causes objects to move in a circle?

Objects move in a circle due to a force acting towards the centre of the circle, known as centripetal force.

In more detail, circular motion is a complex type of movement that objects undergo when a force is applied in a direction towards the centre of the circle. This force is known as the centripetal force. The word 'centripetal' comes from Latin words 'centrum' meaning 'centre' and 'petere' meaning 'to seek', which perfectly describes the nature of this force. It's always directed towards the centre of the circle and is responsible for keeping the object in circular motion.

The centripetal force can be provided by various means depending on the context. For example, in the case of a car moving in a circular path, the friction between the car's tyres and the road provides the necessary centripetal force. In the case of a planet orbiting a star, the gravitational pull of the star provides the centripetal force. For an object being swung around in a circle on a string, the tension in the string provides the centripetal force.

It's important to note that the centripetal force is not a new kind of force, but rather a role that other forces can play. It's also worth mentioning that the object in circular motion is constantly accelerating, even if its speed remains constant. This is because acceleration is a change in velocity, and velocity is a vector quantity that includes both speed and direction. Since the direction of the object's motion is constantly changing in circular motion, the object is always accelerating towards the centre of the circle.

In summary, any object moving in a circle is experiencing a centripetal force towards the centre of the circle. This force could be provided by gravity, tension, friction, or any other force, depending on the situation. The object is also constantly accelerating due to the continuous change in direction of motion.