Question

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

• A. 2 N
• B. 4 N
• C. 6 N
• D. 8 N

Answer 1

Answer: (C)

6 N

Answer 2

The total torque about $O$ is given by or $\tau =F_{1} d+F_{2} d-F_{3} d$ $\Rightarrow F_{3} =F_{1}+F_{2}$ $=4+2$ $=6\, N$ Here, $d$ is the perpendicular distance of $O$ from every side of the equilateral triangle.