If excess of pressure inside a soap bubble of radius 2 cm is balanced by that due to column of oil of (specific gravity =0.8 ) 2 mm high. What is the surface tension of soap bubble?

Question

If excess of pressure inside a soap bubble of radius 2 cm is balanced by that due to column of oil of (specific gravity =0.8 ) 2 mm high. What is the surface tension of soap bubble? (A) 12 × 102 N / m (B) 6 × 10-2 N / m (C) 8.12 × 10-2 N / m (D) 7.84 × 10-2 N / m

Tardigrade Admin · Accepted Answer

P = h ρ g =2 × 10-3 × 0.8 × 103 × 9.8 (sp. gravity .=(ρℓ/ P w )) P=15.68 Pa For soap bubble. P =(4 S / R ) ⇒ 15.68=(4 × S /2 × 10-2) ∴ S =7.84 × 10-2 N / m

Q. If excess of pressure inside a soap bubble of radius $2 c m$ is balanced by that due to column of oil of (specific gravity $= 0.8$ ) $2 mm$ high. What is the surface tension of soap bubble?

$12 \times 1 0^{2} N / m$

$6 \times 1 0^{- 2} N / m$

$8.12 \times 1 0^{- 2} N / m$

$7.84 \times 1 0^{- 2} N / m$

$P = h ρ g$
$= 2 \times 1 0^{- 3} \times 0.8 \times 1 0^{3} \times 9.8$ (sp. gravity $= \frac{ρ _{ℓ}}{P _{w}})$
$P = 15.68 P a$
For soap bubble. $P = \frac{4 S}{R}$
$\Rightarrow 15.68 = \frac{4 \times S}{2 \times 1 0 ^{- 2}}$
$∴ S = 7.84 \times 1 0^{- 2} N / m$

Q. If excess of pressure inside a soap bubble of radius 2cm is balanced by that due to column of oil of (specific gravity =0.8 ) 2mm high. What is the surface tension of soap bubble?

12×102N/m

6×10−2N/m

8.12×10−2N/m

7.84×10−2N/m