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

About 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

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.

Details About Circular Motion

  • 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
    • Radial (centripetal) acceleration
  • In case of this motion, there is some tangential acceleration due to which the speed of particle increases or decreases.
  • The resultant acceleration is the vector sum of radial acceleration and tangential acceleration.

Uniform Circular Motion Examples

  • Motion of artificial satellites around the earth is an example of uniform circular motion. The gravitational force from the earth makes the satellites stay in the circular orbit around the earth.
  • The motion of electrons around its nucleus.
  • The motion of blades of the wind mills.
  • The tip of second՚s hand of a watch with circular dial shows uniform circular motion.

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