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A thin metal disc of radius r floats on ...

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

`2pirTcos theta`

B

`2 pirT`

C

`2pirTcos theta+w`

D

`2pirTcos theta-w`w

Text Solution

Verified by Experts

The correct Answer is:
C
When water is depressed downwards at point of contact, then theforce due ot surface tension acts upwards.
Therefore, apparent weight
`=F_(T)+w`
`=2piT cos theta +w`
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