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प्रश्न
Describe an experiment to prove that friction depends on the nature of a surface.
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उत्तर
To understand the frictional force between the layers of liquid in motion.
- Materials required: Different kinds of liquid (coconut oil, honey, water, ghee), glass plates – 4 nos.
- Procedure:
a. Take a small number of different kinds of liquid like coconut oil, honey, water, and ghee, etc., in a cup.
b. Place one drop of each liquid on a separate glass plate.
c. Next, gently raise one end of the glass plate, one by one, so as to allow the liquid to slide down the smooth surface of the plate.
c. Observe the speed of each liquid. - Observation:
Each liquid moves at a different speed. Water flows faster than other liquids. Coconut oil flows at a moderate speed. Ghee flows very slowly. - Inference:
Between the layers of each liquid, in motion, there is a frictional force parallel to the layers of the liquid. This frictional force opposes the motion of the liquid layers while they are in motion.
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[Take surface tension of water T = 7.3 × 10-2 Nm-1, angle of contact = 0, g = 10 ms-2 and density of water = 1.0 × 103 kgm-3]
