NEET
- Exam
- NEET
- Subject
- Physics
- Chapter
- Mechanical Properties of Fluids
NEET · Physics · Mechanical Properties of Fluids
The gauge pressure inside a soap bubble of surface tension T is...
The gauge pressure inside a soap bubble of surface tension is equal to the pressure exerted by a liquid column of density and height . What is the work done in blowing this soap bubble from zero radius? (Let be the acceleration due to gravity)
Options
- A
- B
- C
- D
Correct answer
B.
Step-by-step solution
Excess pressure inside a soap bubble is given by , where is the radius of the bubble.
Gauge pressure exerted by a liquid column of height and density is .
Equating the two pressures as given:
The work done in blowing a soap bubble from zero radius is equal to its surface energy. Since a soap bubble has two free surfaces (inner and outer), the work done is:
Substituting the value of into the work equation:
Note: Using (forgetting the two surfaces for work) leads to the incorrect option , and using (forgetting two surfaces for pressure) leads to the incorrect option .
Answer:
Gauge pressure exerted by a liquid column of height and density is .
Equating the two pressures as given:
The work done in blowing a soap bubble from zero radius is equal to its surface energy. Since a soap bubble has two free surfaces (inner and outer), the work done is:
Substituting the value of into the work equation:
Note: Using (forgetting the two surfaces for work) leads to the incorrect option , and using (forgetting two surfaces for pressure) leads to the incorrect option .
Answer: