A liquid of density $1.1\,\mathrm{g\,cm^{-3}}$ climbs to a height of 5.0 cm when a capillary with internal radius of 0.2 mm is dipped into it. The surface tension (in $\mathrm{N\,m^{-1}}$) of the liquid is closest to
(a)0.05
(b)0.108
(c)0.018
(d)0.005
Answer
SELF-PRACTICE — the source book printed no answer.
Nothing is invented here, so this question has no answer on record.
Explanation
The height of the column at equilibrium is given by $h=\dfrac{2\gamma}{r\rho g}$, so $\gamma=\dfrac{h r \rho g}{2}$.$\rho=1.1\times10^{3}\,\mathrm{kg\,m^{-3}}$, $h=5.0\times10^{-2}\,\mathrm{m}$, $r=0.2\times10^{-3}\,\mathrm{m}$.$\gamma=0.053\,\mathrm{N\,m^{-1}}$, closest to option (1), 0.05.