question_answer

A 20 cm long capillary tube is dipped in water. The water rises up to 8 cm. If the entire arrangement is put in a freely falling elevator, what will be the length of water column in the capillary tube?      

Answer:

                In the freely falling elevator, the entire arrangement is in a state of weightlessness, i.e., \[g=\text{ }0\]. So water will rise in the tube \[\left( h=\frac{2\sigma \cos \theta }{r\rho g} \right)\]to fill the entire 20 cm length of the tube.