Equilibrium of Concurrent Force System

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.