## Mechanical Properties of Fluids Questions and Answers Part-3

1. The property of surface tension is obtained in
a) Solids, liquids and gases
b) Liquids
c) Gases
d) Matter

Explanation: Liquids

2. The surface tension of a liquid
a) Increases with area
b) Decreases with area
c) Increase with temperature
d) Decrease with temperature

Explanation:

3. If two glass plates are quite nearer to each other in water, then there will be force of
a) Attraction
b) Repulsion
c) Attraction or repulsion
d) None of the above

Explanation: Due to force of attraction it is not easier to separate the two glass plates.

4. On mixing the salt in water, the surface tension of water will
a) Increase
b) Decrease
c) Remain unchanged
d) None of the above

Explanation: Soluble impurities increases the surface tension.

5. The maximum force, in addition to the weight required to pull a wire of 5.0 cm long from the surface of water at temperature 20oC, is 728 dynes. The surface tension of water is
a) 7.28 N/cm
b) 7.28 dyne/cm
c) 72.8 dyne/cm
d) $7.28×10^{2} dyne/cm$

Explanation:

6.Consider a liquid contained in a vessel. The liquid solid adhesive force is very weak as compared to the cohesive force in the liquid. The shape of the liquid surface near the solid shall be
a) Horizontal
b) Almost vertical
c) Concave
d) Convex

Explanation: Cohesive force > Adhesive force, so shape of liquid surface near the solid would be convex. For example mercury surface in glass capillary is convex.

7. At which of the following temperatures, the value of surface tension of water is minimum
a) $4^{\circ} C$
b) $25^{\circ} C$
c) $50^{\circ} C$
d) $75^{\circ} C$

Explanation: Surface tension decreases with increase in temperature.

8. If a glass rod is dipped in mercury and withdrawn out, the mercury does not wet the rod because
a) Angle of contact is acute
b) Cohesion force is more
d) Density of mercury is more

Explanation: Cohesion force is more

9. Mercury does not wet glass, wood or iron because
a) Cohesive force is less than adhesive force
b) Cohesive force is greater than adhesive force
c) Angle of contact is less than $90^{\circ}$
d) Cohesive force is equal to adhesive force