3. Coplanar concurrent point: In this system, line of action of all forces pass through a single point and forces lie in the same plane. An example is the weight suspended by two inclined strings. Here, all the three forces acting on a particle pass through point O. The moment of the forces about the point O is zero. Hence, second condition of (2.1) is already satisfied and only first condition needs to be checked.

Equation of equilibrium

	3. Coplanar concurrent point: In this system, line of action of all forces pass through a single point and forces lie in the same plane. An example is the weight suspended by two inclined strings. Here, all the three forces acting on a particle pass through point O. The moment of the forces about the point O is zero. Hence, second condition of (2.1) is already satisfied and only first condition needs to be checked.	4. Coplanar non-concurrent forces: All forces do not meet at a point, but lie in a single plane. An example is a ladder resting against wall when a person stands on a rung, which is not at its center of gravity. In this case, for equilibrium, both the conditions of ladder need to be checked.