Question

A disc of paper of radius r is floating on the surface of water of surface tension T. Then force of surface tension on the disc is:

• A. $T.\pi r$
• B. $T.2\pi r$
• C. $T.4\pi r$
• D. $\frac{T}{2\pi r}$

Answer 1

Answer: (B)

$T.2\pi r$

Surface tensions acts along the boundary.
Force $=T.\left(2\pi r\right)$