Concepts Of Physics MCQ Edition [Volume 1]PhysicsSome Mechanical Properties of Matter
When additional air is forced into a soap bubble, the pressure inside it
Options
- Adecreases
- Bincreases
- Cremains unchanged
- Dbecomes zero
Correct answer
A. decreases
Step-by-step solution
The pressure inside a soap bubble of radius R and surface tension T is given by P = P₀ + 4T R , where P₀ is the atmospheric pressure. When additional air is forced into the soap bubble, its size increases, meaning its radius R increases. Since the excess pressure P = 4T R is inversely proportional to the radius, an increase in R leads to a decrease in the excess pressure. Therefore, the total pressure inside the soap bubble decreases.