# Introduction to Uniform Circular Motion, Details About Circular Motion (For CBSE, ICSE, IAS, NET, NRA 2022)

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# Introduction to Uniform Circular Motion

• Circular motion is the motion of a body following a circular path.
• Uniform circular motion is a specific type of circular motion in which the motion of a body following a circular path is at a constant speed.
• The speed is constant but the velocity changes.
• The body has a fixed central point and remains equidistant from it at any given position.
• If a particle is moving in a circle, it must have some acceleration acting towards the centre which is making it move around the centre.
• When an object goes around in a circle, the description of its motion becomes interesting in many ways.

### Uniform Circular Motion

• Suppose you have a ball attached to a string and you move it constantly in a circular motion.
• Then we observe two things:
• The speed of the ball is constant. It traces a circle with a fixed center.
• At every point of its motion, the ball changes its direction. Therefore, we can say that in order to stay on a circular path, the ball has to change its direction continuously.
• We call this acceleration centripetal acceleration (or radial acceleration) , and the force acting towards the centre is called centripetal force.
• In case of uniform circular motion, the acceleration is:

If the mass of the particle is m, we can say from second law of motion that:

## Centripetal vs. Centrifugal Force

• An object in circular motion is kept in circle due to a centripetal force. A centripetal force is a force directed towards the center of a circle. But this seems to go contrary to a lot of people՚s experiences.
• The force is away from the center of the circle, not towards it. This is the definition of a centrifugal force, a force pointing away from the center of a circle.

• This is not a special force, like tension or friction may be a cause of origination of centripetal force.
• When the vehicles turn on the roads, it is the frictional force between tyres and ground which provides the required centripetal force for turning.
• So, if a particle is moving in uniform circular motion:
• Its speed is constant
• Velocity is changing at every instant
• There is no tangential acceleration