Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by 75 × 10-4 N, forces due to the weight of the liquid. If the surface tension of water is 6 × 10-2 N/m, the inner-circumference of the capillary must be Option 1) $1.25\times10^{-2}m$ Option 2) $0.50\times10^{-2}m$ Option 3) $6.5\times10^{-2}m$ Option 4) $12.5\times10^{-2}m$

As we discussed in concept @14048

Capillary -

If a tube of very narrow bore is dipped in a liquid, the liquid in the capillary either ascends or descends .

- wherein

A towel soaks water.

Total upward force =circumference $\times surface\: tension$

$=circumference\times 6\times 10^{-2}$

Total upward force = weight of the liquid

$=circumference\times 6\times 10^{-2}=75\times 10^{-4}$

$circumference =\frac{75\times 10^{-4}}{6\times 10^{-2}}$

$=12.5\times 10^{-2}m$

Option 1)

$1.25\times10^{-2}m$

Option is incorrect

Option 2)

$0.50\times10^{-2}m$

Option is incorrect

Option 3)

$6.5\times10^{-2}m$

Option is correct

Option 4)

$12.5\times10^{-2}m$

Option is incorrect

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