Question

proof for lami's theorem

Answer 1

Lami's theorem states that, if three concurrent forces act on a body keeping it in Equilibrium, then each force is proportional to the sine of the angle between the other two forces.

Let P, Q, R be the 3 concurrent forces in equilibrium as shown in fig. (a)

Since the forces are vectors, we can move them to form a triangle as shown in fig. (b)



Applying sine rule we get

P/(sin(180−α))=Q/(sin(180−β))=R/(sin(180−θ))P/(sinα)=Q/(sinβ)=R/(sinθ)...... Hence Proved