Observing uniform circular motion in Motion – Class 9 Science Experiment

Chapter Name: Motion

Activity Name: Observing uniform circular motion in Motion

Activity Description:

Observing uniform circular motion in Motion - Class 9 Science Experiment

Whirling a stone tied to the end of a string continuously to observe its motion.

Required Items:

  1. Stone, string, a safe open space

Step by Step Procedure:

  1. Tie one end of the string securely to the stone and the other end to a fixed point.
  2. Stand in an open space with the stone at arm’s length.
  3. Start whirling the stone in a circular path by rotating your hand continuously.
  4. Maintain a constant speed while whirling the stone.
  5. During the motion, draw the path of the stone’s motion on the ground or on a piece of paper.
  6. Mark different positions of the stone on the path and also draw the velocity vectors at those positions as shown in Figure 16.

Experiment Observations:

  1. The path of the stone is circular.
  2. The direction of velocity changes at every instant, but the speed remains constant.


  • Ensure there are no obstacles or people around while performing the activity to avoid accidents.
  • Keep a safe distance from others to avoid hitting someone accidentally with the stone.
  • Do not whirl the stone with excessive force to prevent the string from breaking or the stone from flying off uncontrollably.

Lesson Learnt from Experiment:

The experiment demonstrates that when an object moves in a circular path with a constant speed, its velocity is continually changing. This is because velocity is a vector quantity that includes both speed and direction.

Even if the speed remains the same, as long as the direction changes, the velocity is considered to be changing. This is typical of uniform circular motion, where the speed is constant, but the direction changes continuously, resulting in a circular path.

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