Equilibrant force

In mechanics, an equilibrant force is a force which brings a body into mechanical equilibrium. According to Newton's second law, a body has zero acceleration when the vector sum of all the forces acting upon it is zero:

${\displaystyle \sum \mathbf {F} =m\mathbf {a}$ ;\quad \sum \mathbf {F} =0\ \ \Rightarrow \ \ \mathbf {a} =0}

Therefore, an equilibrant force is equal in magnitude and opposite in direction to the resultant of all the other forces acting on a body. The term has been attested since the late 19th century.