A circular ring has inner and outer radii equal to `10 mm and 30 mm` respectively Mass of the ring is `m = 0.7` g. It gently pulled out vertically from a water surface by a sensitive spring. When the spring is stretched `3.4 cm` from its equilibrium position the ring is on verge of being pulled out from the water surface. If spring constant is `k = 0.7 Nm^(–1)` find the surface tension of water.

Answer

`0.076Nm^(-1)`