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

Question

A square wire frame of size L is dipped in a liquid. On taking out, a membrane is formed. If the surface tension of liquid is T, the force acting on the frame will be : (A) 2 TL (B) 4 TL (C) 8 TL (D) 10 TL

Tardigrade Admin · Accepted Answer

The surface tension of a liquid is defined as the force per unit length in the plane of the liquid surface, acting at right angles on either side of an imaginary line drawn on that surface. Thus,
Since, membrane has two free surfaces,
total force acting is given by

F = 2 \times T \times

boundary of frame

F = 2 T \times 4 L

F = 8 T L

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

2 TL

4 TL

8 TL

10 TL

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