Between a frame and a light slider, a thin film of soap solution is made. Whose length is `x` and width is `y`. Find surface tension force on the slider. To keep the slider in equilibrium, how much weight should be suspended ?

Explanation

The surface will act like a tight membrane and pull the slider with a force
`F = (T)(l)`
Since this a film, it will have two surfaces: the front surface and the back surface. On the front surface, contact length is `x`, and also on the back surface contact length is `x`. So total contact length will be `l = x + x = 2x`
So surface tension force on slider.
`F = (T)(2x)`
For equilibrium, this force will be balanced by weight of suspended block.
`(T)(2x) = mg`
`m = (2Tx)/(g)`