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Question #42500
The Question
A vertical cylinder of cross-sectional area is completely submerged in a fluid bath. The top of the cylinder is fixed at a depth below the fluid surface. The bottom of the cylinder is sealed by a movable piston of mass and volume . An external mechanism moves the piston to perform a cycle.
The cycle consists of four steps:
- The piston is slowly pushed down, increasing the cylinder's internal volume from to , while the fluid is maintained at .
- The piston is held in place while the fluid is cooled to .
- The piston is slowly pulled up, decreasing the volume from to , while the fluid is maintained at .
- The piston is held in place while the fluid is heated back to .
The fluid density is and . Calculate the magnitude of the net work done BY THE FLUID on the piston during one complete cycle. (Assume and )
Options
- A.
- B.
- C.
- D.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Multi-Concept_Bridge
Master problems that require linking physics and math concepts to solve complex competitive questions.
Concepts Behind This Question
Refrigerator Coefficient of Performance|Mechanical Energy Conservation|Archimedes' Buoyancy Dynamics
Why This Question Is Tricky
Common Mistakes
This question tests the precise application of Archimedes' principle and hydrostatic pressure on a partially exposed submerged boundary.
A common trap is assuming the external pressure is simply and neglecting the buoyant contribution of the piston's own volume (its thickness), which leads to an incorrect pressure head (yielding 320 J).
Another trap is incorrectly subtracting the buoyant force (yielding 280 J).
Additionally, students often fail to integrate the pressure over the varying depth, incorrectly treating the hydrostatic pressure as constant during the expansion phase.
By asking for the work done specifically by the fluid, it isolates the mechanical-hydrostatic coupling from the thermodynamic gas laws.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Thermodynamics - Class 11 Part 2 |
| Concept | Refrigerator Coefficient of Performance |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |