# Rise of Water in a 20 cm Capillary Tube

• vissh
In summary, the discussion is about a capillary tube being dipped in water and the water rising to a certain height. The question is whether in a free falling elevator, the water will overflow or remain at the same height. The conclusion is that due to the adhesive force and surface tension, the water will form a hemispherical surface at the end of the tube and not overflow. The orientation of the hemisphere depends on the capillary tube and the liquid used.

hello :)

## Homework Statement

(Q)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, the length of water column in the capillary tube will be
<a>8 cm <b>6 cm <c>10 cm <d>20 cm

## The Attempt at a Solution

From the elevator frame, the fluid will be weightless and only force on the "fluid in capillary's" upper part will be S[2(pie)r]cosA upwards{where A is the contact angle}
It will make the fluid rise and rise and reach 20 cm.
I want to ask will the fluid then overflow or will remain at the 20 cm mark.
I think It will overflow as the accleration will be upwards and even if the acceleration vanishes, due to velocity gained by fluid,it should overflow.
What you think oO

The adhesive force and the surface tension are independent of gravitational force. when the liquid reaches the en of the tube, instead of overflowing, it forms a hemispherical surface. At the edge, force due to surface tension balance the adhesive force between liquid and glass. hence the liquid doe not overflow.

Thanks :)
One more question :- Will the hemisphere upwards or downwards?? Or it depends on capillary tube and the liquid taken??

vissh said:
Thanks :)
One more question :- Will the hemisphere upwards or downwards?? Or it depends on capillary tube and the liquid taken??
Hemisphere will be upwards except in mercury. but mercury will not rise in the capillary.

Thanku :)

vissh said:
Thanku :)

welcome.