The resultant of two forces of equal magnitudes is also equal to the magnitude of the forces. The angle between the two forces is________________?
Correct answer: D. 120°
- A. 30°
- B. 60°
- C. 90°
- D. 120°
Explanation
For two forces of equal magnitude F, the resultant obeys R² = F² + F² + 2F²cosθ. Setting R = F gives F² = 2F² + 2F²cosθ, so cosθ = -1/2 and θ = 120°. Option c would be obtained by ignoring the direction effect of the angle and treating the forces as perpendicular.
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Vector addition combines directed quantities using the head-to-tail, parallelogram and component methods. Work includes finding the resultant magnitude and direction for two or more vectors, resolving vectors into perpendicular components, and distinguishing vector addition from scalar addition, where direction has no role.
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