Question

A film of water is formed between two straight parallel wires of length $10cm$ each, separated by $0.5cm$. If their separation is to be increased by $1mm$, while still maintaining their parallelism, how much work will have to be done? $[T=7.2\times {10}^{-2}N/m]$

Answer 1

Work done,

W = 2t $\Delta$ A

surface tension, T = $7.2\times {10}^{-2}$ N / m

W = $2\times 7.2\times {10}^{-2}\times \left[\right(10\times {10}^{-2}\times 0.6\times {10}^{-2})-(10\times {10}^{-2}\times 0.5\times {10}^{-2}\left)\right]$

W = $14.4\times {10}^{-2}\times {10}^{-4}[6-5]$

W = $1.44\times {10}^{-5}$ J