Question

A capillary tube of radius $r$ can support a liquid of weight $6.28 \times 10^{-4} \,N$. If the surface tension of the liquid is $5 \times 10^{-2} \,N / m$. The radius of capillary must be

• A. $2.0 \times 10^{-3} m$
• B. $20 \times 10^{-4} m$
• C. $1.5 \times 10^{-3} m$
• D. $12.5 \times 10^{-4} m$

Answer 1

Answer: (A)

$W=T . 2 \pi r$
$ r =\frac{W}{2 \pi T}=\frac{6.28 \times 10^{-4}}{2 \times 3.14 \times 5 \times 10^{-2}} $
$=2 \times 10^{-3} m$