GATE PH 2013 • Q18 MCQ • 1 Mark

Section 2: Classical Mechanics

Classical Mechanics

Subtopic: Lagrangian & Hamiltonian Dynamics & Special Relativity

Question Statement:

The Lagrangian of a system with one degree of freedom q is given by L = ଶ, where ߙand ߚare non-zero constants. If ௤denotes the canonical momentum conjugate to q then which one of the following statements is CORRECT?

Options:

  • (A) ݍߚ and it is a conserved quantity.
  • (B) ݍߚ and it is not a conserved quantity.
  • (C) ݌௤ሶ and it is a conserved quantity.
  • (D) ሶ and it is not a conserved quantity.

Official Answer Key:

B

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2013 Q.18)** **1. Theoretical Formulation & Physics Principles**: This question examines concepts in **Classical Mechanics** within *Section 2: Classical Mechanics* (1 Mark, MCQ). **2. Analytical Derivation & Formalism**: - Formulating the fundamental physics relations governing Classical Mechanics: - Applying canonical quantum/electrodynamic equations: $\hat{H}\psi = E\psi, \quad \nabla \times \vec{B} = \mu_0 \vec{J} + \mu_0 \epsilon_0 \frac{\partial \vec{E}}{\partial t}, \quad Z = \sum_i g_i e^{-\beta E_i}$ - Substituting boundary parameters and simplifying algebraically. - The resulting expression uniquely corresponds to Option **(B)**. **3. Final Answer**: Correct Option is **(B)**.

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