A film of water is formed between two straight parallel wires each 10 cm long and at separation 0.5 cm. The work required to increase 1 mm distance between the wires is p × 10-5 J. Find p. (Surface tension =72 × 10-3 N / m )

Question

A film of water is formed between two straight parallel wires each 10 cm long and at separation 0.5 cm. The work required to increase 1 mm distance between the wires is p × 10-5 J. Find p. (Surface tension =72 × 10-3 N / m ) (A)  (B)  (C)  (D)

Tardigrade Admin · Accepted Answer

<img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/3de855620b17473e3349e4f197f9a509-.png" /> The process is shown in the figure. As we have to produce 2 films, so Δ W=2(Δ A) T =2[10 cm × 0.6 cm -10 cm × 0.5 cm ] × 72 × 10-3 N / m =2 ×(10 × 10-2 m )(0.1 × 10-2 m ) × 72 × 10-3 N / m =1.44 × 10-5 J =2[10 cm × 0.6 cm -10 cm × 0.5 cm ] × 72 × 10-3 N / m =2 ×(10 × 10-2 m )(0.1 × 10-2 m ) × 72 × 10-3 N / m =1.44 × 10-5 J

Q. A film of water is formed between two straight parallel wires each 10cm long and at separation 0.5cm. The work required to increase 1mm distance between the wires is p×10−5J. Find p. (Surface tension =72×10−3N/m )

The process is shown in the figure. As we have to produce 2 films, so ΔW=2(ΔA)T =2[10cm×0.6cm−10cm×0.5cm]×72×10−3N/m =2×(10×10−2m)(0.1×10−2m)×72×10−3N/m =1.44×10−5J =2[10cm×0.6cm−10cm×0.5cm]×72×10−3N/m =2×(10×10−2m)(0.1×10−2m)×72×10−3N/m =1.44×10−5J

Q. A film of water is formed between two straight parallel wires each $10 c m$ long and at separation $0.5 c m$ . The work required to increase $1 mm$ distance between the wires is $p \times 1 0^{- 5} J$ . Find $p$ .
(Surface tension $= 72 \times 1 0^{- 3} N / m$ )