In static, a body is said to be in equilibrium when the force system acting upon it has a zero resultant.
Conditions of Static Equilibrium of Concurrent Forces
The sum of all forces in the x-direction or horizontal is zero.
$\Sigma F_x = 0$ or $\Sigma F_H = 0$
The sum of all forces in the y-direction or vertical is zero.
$\Sigma F_y = 0$ or $\Sigma F_V = 0$
Important Points for Equilibrium Forces
- Two forces are in equilibrium if they are equal and oppositely directed.
- Three coplanar forces in equilibrium are concurrent.
- Three or more concurrent forces in equilibrium form a close polygon when connected in head-to-tail manner.