Question

The sap in tree rises in a system of capillaries of radius $2.5 \times 10^{-5}\, m$. The surface tension of sap is $7.28 \times 10^{-2}\, N \, m^{-1}$ and the angle of contact is $0^{\circ}$. The maximum height to which sap can rise in a tree through capillarity action is $\left(\rho_{sap}=10^{3}\,kg\,m^{-3}\right)$

• A. $0.21 \, m$
• B. $0.59\,m$
• C. $0.87\,m$
• D. $0.91\, m$

Answer 1

Answer: (B)

Here, $r=2.5\times10^{-5}\,m, S=7.28\times10^{-2}\,N m^{-1}$
Angle of contact, $\theta=0^{\circ}, \rho=10^{3}\,kg \, m^{-3}$
The maximum height to which the sap can rise bycapillary action is,
$h=\frac{2S\,cos\,\theta}{r \rho g}=\frac{2\times7.28\times10^{-2}\times cos\,0^{\circ}}{2.5\times10^{-5}\times10^{3}\times9.8}$
$= 0.59\,m$