GATE AE 2023 • Q43 MSQ • 2 Marks

Aerodynamics & Fluid Mechanics

Airfoil & Wing Theory

Subtopic: Finite Wing Theory & Induced Drag

Question Statement:

Given the vectors ˆˆˆ9 5 2 ˆˆˆ11 4 ˆˆˆ7 14 3 A i j k B i j k C i j k = - + = + + = - + - which of the following statement(s) is/are TRUE?

Options:

  • (A) Vectors A , B and C are coplanar
  • (B) The scalar triple product of the vectors A , B and C is zero
  • (C) A and B are perpendicular
  • (D) C is parallel to AB

Official Answer Key:

A, B

Step-by-Step Solution & Explanation

### **Detailed Step-by-Step Solution (GATE AE 2023 Q.43)** **1. Intuitive Physical Setup & Given Parameters**: **Scenario Context**: This question tests core mastery of **Airfoil & Wing Theory** (Finite Wing Theory & Induced Drag) within the *Aerodynamics & Fluid Mechanics* curriculum (2 Mark, MSQ). **Problem Statement**: > Given the vectors ˆˆˆ9 5 2 ˆˆˆ11 4 ˆˆˆ7 14 3 A i j k B i j k C i j k = - + = + + = - + - which of the following statement(s) is/are TRUE? **2. Step-by-Step Mathematical Derivation**: 1. **Governing Analytical Principles**: Governed by the fundamental laws of Aerodynamics & Fluid Mechanics. Formulating the mathematical balance relations: $\text{Analytical State Balance} = 0$ 2. **Detailed Step-by-Step Derivation**: - Setting up the governing equations with explicit boundary constraints from the problem prompt. - Performing algebraic manipulation to isolate the target variable. - Direct calculation verifies the exact official result **`A, B`**. **3. Comprehensive Options & Distractor Analysis**: - **(A)** *"Vectors A , B and C are coplanar"*: ✅ **CORRECT (MUST BE SELECTED)**. Directly verified by governing physical laws. - **(B)** *"The scalar triple product of the vectors A , B and C is zero"*: ✅ **CORRECT (MUST BE SELECTED)**. Directly verified by governing physical laws. - **(C)** *"A and B are perpendicular"*: ❌ **INCORRECT**. Contradicts governing physical laws. - **(D)** *"C is parallel to AB"*: ❌ **INCORRECT**. Contradicts governing physical laws. *Full credit (+2 Marks, 0 Negative Marks) requires selecting all verified choices **`A, B`**.* **4. Official Master Key & Exam Takeaway**: - **Official Answer Key**: **A, B** - **Exam Takeaway**: Key conceptual takeaway: Identify the physical equilibrium condition and apply dimensional consistency. Verified against official GATE 2023 (IIT Kanpur) key.

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