A circular ring of radius 7 cm is supported horizontally from the pan of a balance, so that it comes in contact with the water in a glass vessel. What force will required to detach it from the surface of water. (Surface tention of water =0.072N/m).

A circular ring of radius 7 cm is supported horizontally from the pan

1.	A circular ring of radius 7 cm is supported horizontally from the pan of a balance, so that it comes in contact with the water in a glass vessel. What force will required to detach it from the surface of water. (Surface tention of water =0.072N/m).
Answer» Solution :Neglecting the thickness of the ring, the net DOWNWARD force on the INNER and OUTER circumferenc of the ring dur to SURFACE tesion = `Sxx2pi(R+R)=Sxx4piR` `S=0.072N//m, R=7cm=7x10^(-2)m` The vertical force required to detach it from the water surface is `F=Sxx4piR` `=0.072xx4xx22/7=10^(-2)=6.336xx10^(-2)N`