According to Lami's theorem, if the three forces acting at a point are in equilibrium, then each force is proportional to the sine of the angle between the other two
The moment of a force
is the turning effect produced by a force, on the body, on which it acts
is equal to the product of force acting on the body and the perpendicular distance of a point and the line of action of the force
is equal to twice the area of the triangle, whose base is the line representing the force and whose vertex is the point, about which the moment is taken
If a number of co-planar forces acting at a point be in equilibrium, the sum of clockwise moments must be equal to the sum of anticlockwise moments, about any point.
Varingon's theorem of moments states that if a number of coplanar forces acting on a particle are in equilibrium, then the algebraic sum of their moments about any point is equal to the moment of their resultant force about the same point.
According to the law of moments, if a number of coplanar forces acting on a particle are in equilibrium, then the algebraic sum of their moments about any point in their plane is zero.