Difficulty: Easy
Correct Answer: 0° and 180°
Explanation:
Given data
Two fixed magnitudes P and Q with included angle θ.
Concept/Approach
Resultant magnitude: R = √(P² + Q² + 2PQ cosθ).
Step-by-step
R is maximum when cosθ = 1 ⇒ θ = 0° (same direction).R is minimum when cosθ = −1 ⇒ θ = 180° (opposite directions).
Common pitfalls
Thinking 90° gives minimum; at 90°, R = √(P² + Q²), which is intermediate.
Final Answer
0° and 180°
Discussion & Comments