## Mechanical Properties of Fluids Questions and Answers Part-10

1. A mercury drop does not spread on a glass platebecause the angle of contact between glass and mercury is
a) Acute
b) Obtuse
c) Zero
d) $90^{\circ}$

Answer: b
Explanation: Obtuse

2. A liquid is coming out from a vertical tube. The relation between the weight of the drop W, surface tension of the liquid T and radius of the tube r is given by, if the angle of contact is zero
a) $W=\pi r^{2}T$
b) $W= 2\pi rT$
c) $W= 2r^{2}\pi T$
d) $W=\frac{3}{4}\pi r^{3}T$

Answer: b
Explanation: $W=2\pi rT$

3. The parts of motor cars are polished by chromium because the angle of contact between water and chromium is
a) $0^{\circ}$
b) $90^{\circ}$
c) Less than $90^{\circ}$
d) Greater than $90^{\circ}$

Answer: d
Explanation: Greater than $90^{\circ}$

4. A glass plate is partly dipped vertically in the mercury and the angle of contact is measured. If the plate is inclined, then the angle of contact will
a) Increase
b) Remain unchanged
c) Increase or decrease
d) Decrease

Answer: b
Explanation: Remain unchanged

5. The liquid meniscus in capillary tube will be convex, if the angle of contact is
a) Greater than 90°
b) Less than 90°
c) Equal to 90°
d) Equal to 0°

Answer: a
Explanation: Greater than 90°

6. The value of contact angle for kerosene with solid surface.
a) 0°
b) 90°
c) 45°
d) 33°

Answer: a
Explanation: 0°

7. Nature of meniscus for liquid of 0o angle of contact
a) Plane
b) Parabolic
c) Semi-spherical
d) Cylindrical

Answer: c
Explanation: Semi-spherical

8. A liquid wets a solid completely. The meniscus of the liquid in a sufficiently long tube is
a) Flat
b) Concave
c) Convex
d) Cylindrical

Answer: b
Explanation: Concave

9. What is the shape when a non-wetting liquid is placed in a capillary tube
a) Concave upward
b) Convex upward
c) Concave downward
d) Convex downward

Answer: b
Explanation: Since for such liquid (Non-wetting) angle of contact is obtuse

10. For which of the two pairs, the angle of contact is same
a) Water and glass; glass and mercury
b) Pure water and glass; glass and alcohol
c) Silver and water; mercury and glass
d) Silver and chromium; water and chromium

Answer: b
Explanation: Both liquids water and alcohol have same nature (i.e. wet the solid). Hence angle of contact for both is acute