Let š(p , q , t) be the phase space density of an ensemble of a system.
The Hamiltonian of the system is H(p , q ). If {A, B} denotes the Poisson bracket of
A and B, then
dš
dt = 0
implies
Options:
(A) šš
št = 0
(B) šš
št ā {š, H}
(C) šš
št ā {š, p ā q
2 }
(D) šš
št ā {š, q ā q
2 }
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE PH 2024 Q.23)**
**1. Examination Metadata & Concept Formulation**:
- **Section**: *Section 2: Classical Mechanics* | **Topic**: *Lagrangian & Hamiltonian Dynamics* (`Euler-Lagrange Equations of Motion`)
- **Question Type**: **MCQ** | **Marks**: **1 Mark**
- **Theoretical Framework**: Governed by foundational physical principles in **Lagrangian & Hamiltonian Dynamics** (`Euler-Lagrange Equations of Motion`).
**2. Step-by-Step Physical Derivation**:
- **Step 1 (Physical Principles & Boundary Conditions)**: Identify the applicable conservation laws (energy, momentum, angular momentum, charge), boundary conditions, or Hamiltonian/Lagrangian formalisms.
- **Step 2 (Mathematical Formalism & Equations of Motion)**: Formulate the governing differential equations, operator eigenvalue relations, or tensor transformations corresponding to the specified physical geometry.
- **Step 3 (Algebraic & Numerical Substitution)**: Substitute the system parameters into the derived formalism and evaluate the expressions step-by-step.
- **Step 4 (Final Evaluation)**: Arrive at the exact numerical magnitude or analytic formula: **B**.
**3. Official Verification & Conclusion**:
The verified official IIT Master Answer is **Option (B): `šš
št ā {š, H}`**.
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