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A soap bubble, having radius of 1 mm, is...

A soap bubble, having radius of 1 mm, is blown from a detergent solution having a surface tension of `2.5xx10^(-2)N//m`. The pressure inside the bubble equals at a point `Z_(0)` below the free surface of water in a container. Taking `g=10 m//s^(2)`, density of water `=10^(3) kg//m^(3)`, the value of `Z_(0)` is :

A

0.5cm

B

100 cm

C

10 cm

D

1 cm

Text Solution

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The correct Answer is:
To solve the problem, we need to find the height \( Z_0 \) below the free surface of water where the pressure inside the soap bubble equals the pressure at that point in the water. ### Step-by-Step Solution: 1. **Understand the Pressure Inside the Soap Bubble**: The excess pressure inside a soap bubble is given by the formula: \[ \Delta P = \frac{4T}{R} \] where \( T \) is the surface tension and \( R \) is the radius of the bubble. 2. **Given Values**: - Surface tension \( T = 2.5 \times 10^{-2} \, \text{N/m} \) - Radius of the bubble \( R = 1 \, \text{mm} = 1 \times 10^{-3} \, \text{m} \) 3. **Calculate the Excess Pressure**: Substituting the values into the excess pressure formula: \[ \Delta P = \frac{4 \times (2.5 \times 10^{-2})}{1 \times 10^{-3}} = \frac{1 \times 10^{-1}}{1 \times 10^{-3}} = 100 \, \text{N/m}^2 \] 4. **Pressure at Depth \( Z_0 \)**: The pressure at a depth \( Z_0 \) in a fluid is given by: \[ P = P_A + \rho g Z_0 \] where \( P_A \) is the atmospheric pressure (which will cancel out later), \( \rho \) is the density of the fluid (water), \( g \) is the acceleration due to gravity, and \( Z_0 \) is the depth. 5. **Given Values for Water**: - Density of water \( \rho = 10^3 \, \text{kg/m}^3 \) - \( g = 10 \, \text{m/s}^2 \) 6. **Equate the Pressures**: Since the pressure inside the bubble equals the pressure at depth \( Z_0 \): \[ \Delta P = \rho g Z_0 \] Substituting the known values: \[ 100 = (10^3)(10)Z_0 \] 7. **Solve for \( Z_0 \)**: Rearranging the equation gives: \[ Z_0 = \frac{100}{10^3 \times 10} = \frac{100}{10^4} = 0.01 \, \text{m} \] Converting to centimeters: \[ Z_0 = 1 \, \text{cm} \] ### Final Answer: The value of \( Z_0 \) is \( 1 \, \text{cm} \).

To solve the problem, we need to find the height \( Z_0 \) below the free surface of water where the pressure inside the soap bubble equals the pressure at that point in the water. ### Step-by-Step Solution: 1. **Understand the Pressure Inside the Soap Bubble**: The excess pressure inside a soap bubble is given by the formula: \[ \Delta P = \frac{4T}{R} ...
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