Water flows through a horizontal tube as shown in figure (13-E9). If the difference of heights of water column in the vertical tubes is 2 cm, and the areas of cross section at A and B are 4 cm2 and 2 cm2 respectively, find the rate of flow of water across any section.


Given, area of cross-section of tube A,

area of cross-section of tube B,


Difference in height in the two columns,


Let the speed of water at A be and speed of water at B be .


From the equation of continuity



—————(1)


The pressure difference between A and B is —————(2)


We consider the flow at two points in A and B such that they lie on the same horizontal plane. Applying Bernoulli’s equation,



Using (2)





Therefore, the rate of flow is


1