Before You Begin
Question #42866
The Question
A cylindrical string of length , cross-sectional area , and intrinsic linear mass density is stretched with a constant tension between two rigid supports inside a closed chamber. The chamber is filled with an ideal monoatomic gas (). Due to the fluid's added mass effect, the effective linear mass density of the string during transverse vibrations is given by , where is the density of the gas. Initially, the gas has an energy density (internal energy per unit volume) of and a mass density of . In this initial state, it is given that , and the string's fundamental frequency is . The gas is then rapidly and adiabatically compressed until its energy density becomes . Assuming , , and remain unchanged, what is the new fundamental frequency of the string?
Options
- A.
- B.
- C.
- D.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Intuition_Breaker
Train your brain to resist "obvious" answers that are designed to deceive your intuition.
Concepts Behind This Question
Fundamental Frequency in Strings|Adiabatic Process Constraint|Wave Intensity and Medium
Why This Question Is Tricky
Common Mistakes
This question tests the student's ability to couple thermodynamics with wave mechanics by dynamically updating system constants.
The primary trap lies in the misapplication of the adiabatic constraint and the added mass effect.
Students often incorrectly assume that energy density scales linearly with density (an isothermal assumption, leading to ) or they completely neglect the intrinsic mass of the string when calculating the new wave speed.
By forcing the recalculation of the effective linear mass density using the adiabatic relation and the energy density relation , the problem penalizes rote application of the static string frequency formula and demands rigorous tracking of fluid-structure interactions.
Quick Facts About This Question
Question Information
| Subject | Physics |
| Chapter | Waves - Class 11 Part 2 |
| Concept | Fundamental Frequency in Strings |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |