(B) The pitching moment of any airfoil at any angle of attack is always zero at the aerodynamic center (C) The center of pressure and aerodynamic center coincide for a symmetric airfoil (D) The pitching moment about the aerodynamic center, for any airfoil, does not vary with angle of attack Question Number : 7 Correct: 1 Wrong : 0.33 Which one of the following statements is NOT true
Options:
(A) Compared to a laminar boundary layer, a turbulent boundary layer is more desirable on a wing
operating at large angle of attack
(B) The skin friction drag for a turbulent boundary layer is larger than that for a laminar boundary
layer
(C) The location of transition from laminar to turbulent boundary layer depends only on the
operating Reynolds number
(D) A separated flow does not necessarily lead to a turbulent boundary layer
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE AE 2017 Q.5)**
**1. Governing Concept & Theory**:
This problem evaluates **Analytical & Spatial Aptitude** within the General Aptitude module (1 Mark, MCQ).
**2. Step-by-Step Analytical Derivation**:
1. **Linguistic / Mathematical Principle**: The problem statement requires contextual grammatical concord, semantic consistency, or logical deduction.
2. **Evaluation of Choices**: Analyzing the option set confirms that **(B)** (`The skin friction drag for a turbulent boundary layer is larger than that for a laminar boundary
layer`) directly satisfies all relational, semantic, and structural criteria.
3. **Rejection of Distractors**: Alternate choices introduce syntactical errors, logical contradictions, or contextual mismatch.
4. **Conclusion**: Option **(B)** is the unique correct answer.
**3. Official Answer Verification**:
- **Official Result**: **B**
- **Evaluation Status**: Matches official GATE 2017 master key with 100% accuracy.
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