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A square frame of side L is dipped in a liquid. On taking out, a membrane is formed. If the surface tension of the liquid is T, the force acting on the frame will be  

  • Option 1)

    2 TL

  • Option 2)

    4 TL

  • Option 3)

    8 TL

  • Option 4)

    10 TL

 

Answers (2)

As we learnt in 

Coefficient of viscosity -

 F = nA\frac{du}{dz}

A is the area of contact for liquid layers

\frac{du}{dz} is velocity gradient; the change in velocity with distance.

n is coefficient of viscosity.

 

-

 

Force \: on \: each \: side= 2TL\: \left ( due\: to\: two\: sur\! f\! aces \right )

\therefore Force\: on \: the \: frame= 4\left ( 2TL \right )= 8TL

 


Option 1)

2 TL

Incorrect

Option 2)

4 TL

Incorrect

Option 3)

8 TL

Correct

Option 4)

10 TL

Incorrect

Posted by

subam

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As after dipping the square frame it forms 2 layers of liquid 

1- Frontside,F=T*L

2-Backside,F=T*L

So net force acting on frame will be T*L+T*L=2T*L(1) will be the correct answer

 

Posted by

SUBHODEEP MAITY

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