A thin metal disc of radius r floats on water surface and bends the surface downwards along the perimeter making an angle θ with verticle 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

Question

A thin metal disc of radius r floats on water surface and bends the surface downwards along the perimeter making an angle θ with verticle 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)  2π rT+W  (B)  2π rT cos θ -W  (C)  2π rT cos θ +W  (D)  W-2π rT cos θ

Tardigrade Admin · Accepted Answer

: Weight of disc = upthrust + force due to T =W=2π rT cos θ =2π rT cos θ +W

Q. A thin metal disc of radius r floats on water surface and bends the surface downwards along the perimeter making an angle $θ$ with verticle 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

$2 π r T + W$

$2 π r T cos θ - W$

$2 π r T cos θ + W$

$W - 2 π r T cos θ$

: Weight of disc = upthrust $+$ force due to T $= W = 2 π r T cos θ$ $= 2 π r T cos θ + W$

Q. A thin metal disc of radius r floats on water surface and bends the surface downwards along the perimeter making an angle θ with verticle 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

2πrT+W

2πrTcosθ−W

2πrTcosθ+W

W−2πrTcosθ