Mechanical Properties Of Fluids Ques 8
8. Water rises to a height ’ $h$ ’ in a capillary tube. If the length of capillary tube above the surface of water is made less than ‘h’ then :
[2015 RS]
(a) water rises upto the top of capillary tube and stays there without overflowing
(b) water rises upto a point a little below the top and stays there
(c) water does not rise at all.
(d) Water rises upto the tip of capillary tube and then starts overflowing like fountain.
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Answer:
Correct Answer: 8.(a)
Solution:
- (a) Water rises upto the top of capillary tube and stays there without overflowing.
In case of capillary of insufficient length i.e. $L \angle h$ the liquid will neither overflow from the upper end like a fountain nor it will tickle along the vertical sides of the tube. The liquid after reaching the upper end will increase the radius of its meniscus without changing nature such that
$h r=L r^{\prime} \quad$ (Here, $r$ is the intial radius of tube and $r^{\prime}$ is the new radius)
$\because \quad L<h \quad$
$\because \quad r^{\prime}>r \quad$
BETA
