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A small drop of water of surface tension...

A small drop of water of surface tension S is squeezed between two clean glass plates so that a thin layer of thickness d and area A is formed between them. If the angle of contact is zero, what is the force required to pull the plates apart?

A

` (sigma A )/ (d ) `

B

` (2 sigma A )/( d ) `

C

` (4 sigma A )/(d) `

D

` (8 sigma A )/(d) `

Text Solution

Verified by Experts

The correct Answer is:
B
`because" "` Angle of contact=0
`Rightarrow` Curve AB will be semicircle.
`Rightarrowp'=p_(atm)-(sigma)/(d//2)=p_(atm)-(2sigma)/(d)`
`Rightarrow" ""Force required"=(p_(atm)-p')A=(2sigmaA)/(d)`
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