The radius of an air bubble at the bottom of a lake is $r$,and it becomes $2r$ when the air bubble rises to the top surface of the lake. If $P \text{ cm}$ of water is the atmospheric pressure,then the depth of the lake is: (in $P$)

We are able to squeeze snow and make balls out of it because of

$A$ 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:

$27$ equal small water drops combine to form a big drop. If the surface tension of water is $T$ and the radius of a small drop is $r$,then:
$(A)$ The excess pressure inside the big drop is three times the excess pressure inside the small drop.
$(B)$ Surface energy decreases in this process.
$(C)$ In this process,$72 \pi r^2 T$ energy is released.
$(D)$ The radius of the big drop is $3r$.
The true statements are:

In a water voltameter,the electrolysis of ...... takes place.

State whether the following statements are True or False:
$(i)$ If the weight of a body is greater than the buoyant force of the liquid,the body floats on the surface of the liquid.
$(ii)$ The velocity of water at the bottom of a river is always slower than at the surface.
$(iii)$ The angle of contact increases with an increase in the temperature of the liquid.