The speed with which the earth would have to rotate about its axis so that a person on the equator would weigh $\dfrac{3}{5}$th as much as at present is ($g$ = gravitational acceleration, $R$ = equatorial radius of the earth.)

The excess pressure inside a spherical water drop A is four times that of another water drop B. Then, the ratio of the mass of water drop A to that of drop B is

In a capillary tube of area of cross-section '$a$' water rises to height '$h$'. To what height will water rise in a capillary tube of area of cross-section $4a$?

A soap bubble of radius $\dfrac{1}{\sqrt{\pi}}$ cm is expanded to radius $\dfrac{3}{\sqrt{\pi}}$ cm. Surface tension of soap solution is 25 dyne/cm. The work done during expansion in erg is