According to Lami's Theorem, if three coplanar concurrent forces P, Q, and R keep a body in equilibrium, what relation holds?
Answer and explanation
Correct answer: D. P / sin alpha = Q / sin beta = R / sin gamma
- Step 1: Lami's theorem applies to three concurrent coplanar forces in static equilibrium. Step 2. Each force magnitude is proportional to the sine of the angle between the other two forces: P / sin alpha = Q / sin beta = R / sin gamma. Answer: P / sin alpha = Q / sin beta = R / sin gamma. Why not the others: P + Q + R = 0 is vector sum without scalar relation; cosine relation is invalid; sum of products does not express proportional equilibrium.
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