Question

A ring is cut from a platinum tube 8.5 cm internal and 8.7 cm external diameter. It is supported horizontally from the pan of a balance, so that it comes in contact with the water in a glass vessel. If an extra 3.97. If is required to pull it away from water, the surface tension of water is

• A. True
• B. False

Answer 1

The correct option is B False

$(2\pi r_1+2\pi r_2)\sigma =mg$
$[2\pi x\frac{8.7}{2}+2\pi x\frac{8.5}{2}]\sigma =3.97x980$
$\Rightarrow \sigma =72dynec{m}^{-1}$