Question

how two of the three forces acting on an object in equilibrium. Redraw the diagram, showing all three forces. Label the third force $\overrightarrow{F_3}$.

Short answer

third force is

Step-by-step solution

Step 1.Given information 

Here the figure is given which have two force and from that you identify the third force and redraw the figure.

Step 2

Newton's first law states that if not apply any external force on the object so the it will remain at rest or continues moving with constant speed in a straight line. which is also called the law of equilibrium.

Step 3 

for the equilibrium the net force is Zero

$$\begin{gathered} F_{net}=F_1+F_2+F_3=0 \\ {F}_1(-j)+F_2\left(i\right)+F_{3x}+F_{3y}=0 \\ socomparexandycomponanat \\ {F}_{3x}=-F_2 \\ {F}_{3y}=-F_1 \end{gathered}$$