An annular metal ring of inner radius 7 cm and outer radius 14 cm and negligible weight is floating on the surface of a liquid if surface tension of liquid is `0.08Nm^(-1)` calculate the force required to detach it from liquid surface.

Explanation

The contact length of annular ring with liquid surface
`L=2p0ir_(1)+2pir_(2)rArr L=2xx(22)/(7)xx(14+7)cm`
`L=132 cm=1.32 m.` The force required,
`F=T(L) =0.08xx1.32=0.1056N.`