Question

A thin metal disc of radius r floats on water surface and bends the surface downwards along the perimeter making an angle $\theta$ with vertical edge of the disc If the disc displaces a weight of water W and surface tension of water is T then the weight of metal disc is

• A. $2\pi rT+W$
• B. $2\pi rT\cos \theta -W$
• C. $2\pi rT\cos \theta +W$
• D. $W-2\pi rT\cos \theta$

Answer 1

The correct option is C $2\pi rT\cos \theta +W$

Hence vet downward force

$F_{net}=2\pi r.T\cos \theta +w$