A vessel of area of cross-section A has liquid to a height H. There is a hole at the bottom of vessel having area of cross-section a. The time taken to decrease the level from ${\mathrm{H}}_1$ to ${\mathrm{H}}_2$ will be

1. $\frac{\mathrm{A}}{\mathrm{a}}\sqrt{\frac{2}{\mathrm{g}}}\left[\sqrt{{\mathrm{H}}_1}-\sqrt{{\mathrm{H}}_2}\right]$             

2. $\sqrt{2\mathrm{gh}}$

3. $\sqrt{2\mathrm{gh}({\mathrm{H}}_1-{\mathrm{H}}_2)}$                     

4. $\frac{\mathrm{A}}{\mathrm{a}}\sqrt{\frac{g}{2}}\left[\sqrt{{\mathrm{H}}_1}-\sqrt{{\mathrm{H}}_2}\right]$

A lead shot of 1mm diameter falls through a long column of glycerine. The variation of its velocity v with distance covered is represented by

Water flows through a frictionless duct with a cross-section varying as shown in fig. Pressure p at points along the axis is represented by

From amongst the following curves, which one shows the variation of the velocity v with time t for a small sized spherical body falling vertically in a long column of a viscous liquid -

A liquid does not wet the sides of a solid if the angle of contact is

1. Zero                                     

2. Obtuse (More than 90°)

3. Acute (Less than 90°)           

4. 90°

The meniscus of mercury in the capillary tube is

1. Convex           

2. Concave

3. Plane               

4. Uncertain

At which of the following temperatures, the value of surface tension of water is minimum ?

1. $4°\mathrm{C}$                                       

2. $25°\mathrm{C}$

3. $50°\mathrm{C}$                                     

4. $75°\mathrm{C}$

If a glass rod is dipped in mercury and withdrawn out, the mercury does not wet the rod because 

1. Angle of contact is acute

2. Cohesion force is more

3. Adhesion force is more

4. The density of mercury is more

Mercury does not wet glass, wood or iron because

1. Cohesive force is less than the adhesive force

2. Cohesive force is greater than the adhesive force

3. The angle of contact is less than 90^o

4. Cohesive force is equal to the adhesive force

Surface tension of a liquid is found to be influenced by

1. It increases with the increase of temperature

2. Nature of the liquid in contact

3. Presence of soap that increases it

4. Its variation with the concentration of the liquid