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A circular plate of radius 4 cm and weig...

A circular plate of radius 4 cm and weight W is made to rest on the surface of water. If a minimum pull of W + F is required to clear the plate off the water surface then find F. Given surface tension of water `S_(w) = 0.072 N m^(-1)`

Text Solution

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Radius of the plate = 4 cm = 0.04 m
The downward forces acting on the plate : weight W and force due to surface tension F.
`therefore` Required force, `F = S_(w) xx` circumference of the plate
`= S_(w) xx 2 pi r`
`= 0.072 xx 2 xx pi xx 0.04`
= 0.018 N
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