Question

Assuming the xylem tissues through which water rises from root to the branches in a tree to be of uniform cross-section find the maximum radius of xylem tube in a 10 m high coconut tree so that water can rise to the top. (Surface tension of water = 0.1 N/m, Angle of contact of water with xylem tube = ${60}^0$ )

• A. 1 cm
• B. 1 mm
• C. $10\mu m$
• D. $1\mu m$

Answer 1

The correct option is D $1\mu m$

Using the expression for capillary rise

$r=\frac{2T\cos \theta }{\rho gh}=\frac{2\times 0.1\times \cos {60}^0}{{10}^3\times 10\times 10}={10}^{-6}m=1\mu m$