When is an object said to be in equilibrium?

The sum of three forces $\vec F_1 = 100\,N$,$\vec F_2 = 80\,N$,and $\vec F_3 = 60\,N$ acting on a particle is zero. The angle between $\vec F_1$ and $\vec F_2$ is nearly .......... $^o$

What are concurrent forces? Explain the equilibrium of a particle under the effect of concurrent forces.

$A$ body of mass $2 \ kg$ is suspended as shown in the figure. The tension $T_1$ (in $kg-wt$) in the horizontal string is :-

$A$ body of mass $m$ is suspended by two strings making angles $\theta_1$ and $\theta_2$ with the horizontal ceiling with tensions $T_1$ and $T_2$ respectively. If $T_1 = \sqrt{3} T_2$,then the angles $\theta_1$ and $\theta_2$ are:

If a body is in equilibrium under a set of non-collinear forces,then the minimum number of forces has to be