$A$ small air bubble is at the inner surface of the bottom of a beaker filled with cold water. Now,the water in the beaker is heated. The size of the bubble increases. The reason for this may be:

The shown $H$-shaped apparatus contains an ideal incompressible liquid and has dimensions as shown in the figure. The diameters of the tubes are small compared to $h$ and $R$. The apparatus is rotated with a constant angular velocity $\omega$ about a symmetric vertical axis as shown in the figure. The pressure at point $A$ is

Explain why bullets of a gun are cylindrical in shape.

$A$ $U$-tube has a left limb with a cross-sectional area one-quarter that of the right limb. The tube contains mercury (density $13.6 \text{ g/cm}^3$). The level of mercury in the narrow (left) limb is at a distance of $36 \text{ cm}$ from the upper end of the tube. What will be the rise in the level of mercury in the right limb if the left limb is filled to the top with water (in $\text{ cm}$)? (Density of water = $1 \text{ g/cm}^3$)

Fill in the blanks using the word$(s)$ from the list appended with each statement:
$(a)$ Surface tension of liquids generally . . . with temperatures (increases / decreases)
$(b)$ Viscosity of gases . . . with temperature,whereas viscosity of liquids . . . with temperature (increases / decreases)
$(c)$ For solids with elastic modulus of rigidity,the shearing force is proportional to . . .,while for fluids it is proportional to . . . (shear strain / rate of shear strain)
$(d)$ For a fluid in a steady flow,the increase in flow speed at a constriction follows (conservation of mass / Bernoulli's principle)
$(e)$ For the model of a plane in a wind tunnel,turbulence occurs at a . . . speed for turbulence for an actual plane (greater / smaller)

$Assertion :$ $A$ thin stainless steel needle can float on a still water surface.
$Reason :$ Any object floats when the buoyancy force balances the weight of the object.