List of top Physics Questions on torque asked in AMUEEE

In an equilateral triangle $ABC$, $ F_{1},F_{2} $ and $ F_{3} $ are three forces acting along the sides $AB, BC$ and $AC$ as shown in the given figure. What should be the magnitude of $F_3$, so that the total torque about $ O $ is zero ?

The torque of force $\vec{ F }=(2 \hat{ i }-3 \hat{ j }+4 \hat{ k }) N$ acting at a point $\vec{ r }=(3 \hat{ i }+2 \hat{ j }+3 \hat{ k }) m$ about origin is