A Cylindrical Vessel Of Area Of Cross-section A and Filled With Liquid To A Height Of h1 has A Capillary Tube Of Length 1 And Radius r protruding Horizontally At Its Bottom. If The Viscosity Of Liquid Is , Density  and G = 9.8 M/s2, find The Time In Which The Level Of Water In Vessel Falls To h2.

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Question

A cylindrical vessel of area of cross-section and filled with liquid to a height of h1 has a capillary tube of length 1 and radius r protruding horizontally at its bottom. If the viscosity of liquid is , density  and g = 9.8 m/s2, find the time in which the level of water in vessel falls to h2.

Solution

Correct option is

 

Lat h be the height of water level in the vessel at instant t which decreases by dh in time dt.   

 Rate of flow of water through capillary tube,

            

Further the rate of flow as given by Poiseuille formula, 

          

From eq. (i) and (ii), 

          

Required time is obtained by integrating, 

          

             .  

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