Observing fluid friction in Friction – Class 8 Science Experiment

Chapter Name: Friction

Activity Name: Observing fluid friction in Friction

Activity Description:

Observing fluid friction in Friction - Class 8 Science Experiment

The experiment aims to observe fluid friction by stirring water in a glass and then stopping the stirring motion to witness the gradual decrease in whirl speed until the water comes to a stable state.

Required Items:

  1. A glass of water
  2. A spoon

Step by Step Procedure:

  1. Take a glass of water and place it on a flat surface.
  2. Use a spoon to stir the water vigorously in a circular motion around an axis.
  3. Observe the water whirl as it moves due to the stirring motion.
  4. Stop stirring the water abruptly and pay attention to what happens next.
  5. Notice how the whirling speed of the water gradually decreases until it eventually stops whirling and reaches a stable state.

Experiment Observations:

  1. When stirring the water, it whirls around an axis due to the force applied by the spoon.
  2. After stopping the stirring motion, the whirling speed of the water reduces gradually.
  3. Eventually, the water comes to a stable state with no discernible whirl motion.


  1. Ensure that the glass of water is placed on a stable and flat surface to avoid accidents.
  2. Be careful while stirring the water to prevent spillage.

Lesson Learnt from Experiment:

The force responsible for stopping the rotation of the water is fluid friction, specifically the frictional forces between the liquid layers and between the liquid surfaces that are in contact with the glass surface. This experiment demonstrates how fluids exert force of friction on objects in motion through them, also known as “drag.”

This phenomenon is not only observed in liquids like water but also in gases like air. Objects moving through air or other fluids, such as boats in water or aeroplanes and jets in the air, experience this force of friction or drag, which opposes their motion.

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