Question

Derive the Lamis Theorem.

Answer 1

During the derivation we used sine law of triangle. Lami's theorem states that if three coplanar, concurrent and non-collinear forces are in equilibrium, the magnitude of each force is proportional to the sine of the angle between the other two forces.

Answer 2

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


hope it will help you.