## Mechanical Properties of Fluids Questions and Answers Part-1

1. The value of surface tension of a liquid at critical temperature is
a) Zero
b) Infinite
c) Between 0 and $\infty$
d) Can not be determined

Explanation: Zero

2. The spherical shape of rain-drop is due to
a) Density of the liquid
b) Surface tension
c) Atmospheric pressure
d) Gravity

Explanation: Surface tension

3. Surface tension is due to
a) Frictional forces between molecules
b) Cohesive forces between molecules
d) Gravitational forces

Explanation: Cohesive forces between molecules

4. When there is no external force, the shape of a liquid drop is determined by
a) Surface tension of the liquid
b) Density of liquid
c) Viscosity of liquid
d) Temperature of air only

Explanation: Surface tension of the liquid

5. Soap helps in cleaning clothes, because
a) Chemicals of soap change
b) It increases the surface tension of the solution
c) It absorbs the dirt
d) It lowers the surface tension of the solution

Explanation: Soap helps to lower the surface tension of solution, thus soap get stick to the dust particles and grease and these are removed by action of water.

6. A pin or a needle floats on the surface of water, the reason for this is
a) Surface tension
b) Less weight
c) Upthrust of liquid
d) None of the above

Explanation: Surface tension

7. Coatings used on raincoat are waterproof because
a) Water is absorbed by the coating
b) Cohesive force becomes greater
c) Water is not scattered away by the coating
d) Angle of contact decreases

Explanation: Cohesive force becomes greater

8. If temperature increases, the surface tension of a liquid
a) Increases
b) Decreases
c) Remains the same
d) Increases then decreases

Explanation: Decreases

9. A drop of oil is placed on the surface of water. Which of the following statement is correct
a) It will remain on it as a sphere
b) It will spread as a thin layer
c) It will be partly as spherical droplets and partly as thin film
d) It will float as a distorted drop on the water surface