# A capillary tube of radius r can support a liquid of weight 6.28 × 10-4 N. if the surface tension of the liquid is 5 × 10-2 N/m. the radius of capillary must be Option 1) $2.5\times 10^{-3}m$ Option 2) $2.0\times 10^{-4}m$ Option 3) $1.5\times 10^{-3}m$ Option 4) $2.0\times 10^{-3}m$

As we discussed in concept

Surface Tension -

It is also defined as force per unit length

$T= \frac{F}{l}$

- wherein

$F\rightarrow force$

$l\rightarrow imaginary \: length$

$T=\frac{F}{l}\:\:\:\:\:\:\:l=2 \pi R$

$T=\frac{F}{2 \pi R}\:\:\:\Rightarrow R=\frac{F}{2 \pi T}\:=\:\frac{28\times 10^{-4}}{2\times 3.14\times 5\times 10^{-2}}$

$R\:=\:2\times 10^{-3}$

Option 1)

$2.5\times 10^{-3}m$

This option is incorrect.

Option 2)

$2.0\times 10^{-4}m$

This option is incorrect.

Option 3)

$1.5\times 10^{-3}m$

This option is incorrect.

Option 4)

$2.0\times 10^{-3}m$

This option is correct.

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