Question

A rectangular film of liquid is extended from (4 cm × 2 cm) to (5 cm × 4 cm). If the work done is 3 × 10-4 j, the value of the surface tension of the liquid is

Answer 1

$\mathfrak{\huge{\underline{Answer:}}}$

As there is a rectangular film of liquid there will be two liquid surfaces.

Please refer to the attached photo for your answer.

Answer 2

Answer:

The Correct Answer would be 0.125 N/m. When a rectangular film of liquid is extended from (4 cm × 2 cm) to (5 cm × 4 cm) and the work done is 3×10⁻⁴ joule, then the value of the surface tension of the liquid is 0.125 N/m.

Explanation:

Given: Initial area of rectangular film = Aₐ = 4 cm × 2 cm = 8 cm² = 8×10⁻⁴ m².

Final area of rectangular film = Aₓ = 5 cm × 4 cm = 20 cm² = 20×10⁻⁴ m².

Work done (W) = 3×10⁻⁴ joule

To Find: The value of the surface tension of the liquid.

Now, for liquid film, number of film surfaces are n=2.

From the formula for work done, we have :

Work done = Surface Tension × Change in the surface area × number of film surfaces

That is W = T × ΔA × n

Hence, 3×10⁻⁴ = T × 12×10⁻⁴ × 2

                        T = 0.125 N/m .