A long capillary tube of radius 0.1 cm open at both ends is filled with water and placed vertically. What will be the height of the column of water left in the capillary (in cm)? Given, surface tension of water = 75 dyne cm-1 and density of water = 1 g cm-3. (Take g = 1000 cm/s2)

When a capillary tube filled with water is placed vertically, a column of water of length h will be held by the upper and the lower meniscus of water as shown in figure.If r is radius of the tube, then weight of the water in the tube.mg=πr2hρgThe weight of the liquid is supported by the force due to surface tension in the two menisci i.e. F=2πrT+2πrT=4πrT, where T is surface tension of the water. In equilibrium, mg=F i.e. πr2hρg=4πrTor h=4Trρg=4×750.1×1×1000=3 cm