91Ó°ÊÓ

The forces F₁ and F₂ are at an angle $\mathrm{θ}$with the horizontal axis as shown in the force diagram.

Apply the Newton's first law which states that the object is at rest will continue to remain at rest, or an object that is moving will continue to move in a straight line with constant velocity, if and only if the net force acting on the object is zero.

Here, there are two forces:

$\stackrel{→}{F_1}$is acting towards the left with an angle above the horizontal and

$\stackrel{→}{F_2}$is acting towards the left with an angle below the horizontal.

Both the forces have same magnitude and make an angle $\mathrm{θ}$with the axis.

The resultant force or the net force F will act in the middle of the horizontal axis. It is shown in the below force diagram labelling F.

Since the object is at equilibrium, one must apply the force F₃ opposite to the resultant force F with the same magnitude so that it nullify the net force.

Therefore, the force F₃ must be applied towards the right and parallel to the horizontal axis as shown in the below force diagram: