Advertisements
Advertisements
प्रश्न
Describe an experiment to prove that friction depends on the nature of a surface.
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
The surface tension of water at 0ºc is 75·5 dyne/cm. Find surface tension of water at 25°C. [ α for water = 0·0021/°C ]
Explain why The angle of contact of mercury with glass is obtuse, while that of water with glass is acute
Explain why Water with detergent dissolved in it should have small angles of contact.
The total energy of free surface of a liquid drop is 2π times the surface tension of the liquid. What is the diameter of the drop? (Assume all terms in SI unit).
A big drop of radius R is formed from 1000 droplets of water. The radius of a droplet will be _______
A) 10 R
B) R/10
C) R/100
D) R/1000
Calculate the work done in increasing the radius of a soap bubble in air from 1 cm to 2 cm. The surface tension of soap solution is 30 dyne/cm. (Π = 3.142).
The properties of a surface are different from those of the bulk liquid because the surface molecules
(a) are smaller than other molecules
(b) acquire charge due to collision from air molecules
(c) find different type of molecules in their range of influence
(d) feel a net force in one direction.
Find the surface energy of water kept in a cylindrical vessel of radius 6.0 cm. Surface tension of water = 0.075 J m−2.
For a surface molecule ______.
- the net force on it is zero.
- there is a net downward force.
- the potential energy is less than that of a molecule inside.
- the potential energy is more than that of a molecule inside.
The sufrace tension and vapour pressure of water at 20°C is 7.28 × 10–2 Nm–1 and 2.33 × 103 Pa, respectively. What is the radius of the smallest spherical water droplet which can form without evaporating at 20°C?
