The lower end of a capillary tube is dipped into water and it is seen that the water rises through 7.5 cm in the capillary. Find the radius of the capilary. Surface tension of water `=7.5xx10^-2Nm^-1`. Contact angle between water and glass `=0^@. Take g=10ms^-2`.

Explanation

We have, `
h=(2Scostheta)/(r rhog)`
or `r=(2Scostheta)/(h rhog)`
`=(2xx(7.5xx10^-2Nm^-1)xx1)/((0.075m)xx(1000kgm^-3)xx(10ms^-2))`
`=2xx10^-4m=0.2mm`.