In general coplanar force system, the number of unknowns that can be found out is

In a general coplanar force system, the forces act in a single plane, so the conditions of equilibrium are applied in that plane.

For a rigid body in 2D equilibrium, we have three independent equations of equilibrium:

1. ΣFx = 0 (Sum of all horizontal forces is zero)

2. ΣFy = 0 (Sum of all vertical forces is zero)

3. ΣM = 0 (Sum of moments about any point is zero)

These three equations allow us to find a maximum of 3 unknowns in the system.

Therefore, the number of unknowns that can be determined is 3.