# A small air bubble of 0.1 mm diameter is formed just below the surface of water. If surface tension of water…

Q: A small air bubble of 0.1 mm diameter is formed just below the surface of water. If surface tension of water is 0.072 Nm-1, the pressure inside the air bubble in kilo Pascal is (Atmospheric pressure = 1.01 × 105 pa)

(a) 28.9

(b) 0.289

(c) 0.0289

(d) 103.88

Ans: (d)

Sol: Pressure inside $\displaystyle P_{in} = P_0 + \frac{2 S}{r}$

Since $\displaystyle \frac{2 S}{r} = \frac{2\times 0.072}{0.1 \times 10^{-3}/2}= 2880 Pa = 2.88 kPa$

$\displaystyle P_{in} = 101 + 2.88$

= 103.88 kPa