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The gas inside a spherical bubble expand...

The gas inside a spherical bubble expands uniformly and slowly so that its radius increases from `R` to `2R`. Let the atmospheric pressure be `p_(0)` and surface tension be `S`. The work done by the gas in the process is

A

`(28piR^3P_0)/3+24pisR^2`

B

`(25piR^3P_0)/3+24pisR^2`

C

`(25piR^3P_0)/3+(23pisR^2)/2`

D

`23piR^2`

Text Solution

AI Generated Solution

The correct Answer is:
To find the work done by the gas in expanding from a radius \( R \) to \( 2R \) in a spherical bubble, we need to consider both the work done against the atmospheric pressure and the work done against the surface tension of the bubble. ### Step-by-Step Solution: 1. **Identify the Work Done Against Atmospheric Pressure:** The work done by the gas against the atmospheric pressure \( p_0 \) when the radius increases from \( R \) to \( 2R \) can be expressed as: \[ W_{\text{pressure}} = \int_{R}^{2R} 4\pi r^2 p_0 \, dr \] Here, \( 4\pi r^2 \) is the surface area of the bubble, and \( p_0 \) is the atmospheric pressure. 2. **Calculate the Work Done Against Surface Tension:** The work done against the surface tension \( S \) is given by: \[ W_{\text{surface}} = \int_{R}^{2R} 4S \, dr \] The factor \( 4S \) comes from the fact that the surface area increases as the bubble expands. 3. **Combine the Work Done:** The total work done by the gas during this process is the sum of the work done against pressure and surface tension: \[ W_{\text{total}} = W_{\text{pressure}} + W_{\text{surface}} \] 4. **Perform the Integration:** - For the work done against atmospheric pressure: \[ W_{\text{pressure}} = 4\pi p_0 \int_{R}^{2R} r^2 \, dr = 4\pi p_0 \left[ \frac{r^3}{3} \right]_{R}^{2R} = 4\pi p_0 \left( \frac{(2R)^3}{3} - \frac{R^3}{3} \right) \] \[ = 4\pi p_0 \left( \frac{8R^3 - R^3}{3} \right) = 4\pi p_0 \left( \frac{7R^3}{3} \right) = \frac{28\pi p_0 R^3}{3} \] - For the work done against surface tension: \[ W_{\text{surface}} = 4S \int_{R}^{2R} dr = 4S [r]_{R}^{2R} = 4S (2R - R) = 4S R \] 5. **Final Expression for Total Work Done:** Combining both contributions: \[ W_{\text{total}} = \frac{28\pi p_0 R^3}{3} + 4S R \] ### Final Answer: The total work done by the gas in the process is: \[ W = \frac{28\pi p_0 R^3}{3} + 4S R \]
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