Question

If the surface tension of a soap solution is 3 × 10^-2 N/m then the work done in forming a soap film of 20 cm × 5 cm will be ______.

Options

• 6 × 10^-2 J

• 6 J

• 6 × 10^-4 J

• 3 × 10^-3 J

Answer 1

If the surface tension of a soap solution is 3 × 10^-2 N/m then the work done in forming a soap film of 20 cm × 5 cm will be 6 × 10^-4 J.

Explanation:

Given, surface tension, T = 3 × 10^-2 N/m

and surface area of soap film, A = 20 cm × 5 cm

= 100 cm²

= 100 × 10^-4 m²

The work done in forming a soap film, W = 2(TA)

= 2(3 × 10^-2 × 100 × 10^-4)

= 6 × 10^-4 J