Q123 / 200 · NEET 2012 (Screening) · Physics

$A B C$ is an equilateral triangle with $O$ as its centre. $\mathrm{F}_1, \mathrm{~F}_2$ and $\mathrm{F}_3$ represent three forces acting along the sides $A B, B C$ and $A C$ respectively. If the total torque about $O$ is zero then the magnitude of $\mathrm{F}_3$ is Figure

  • Correct answer
    A
    $F_1+F_2$
  • B
    $F_1-F_2$
  • C
    $\frac{F_1+F_2}{2}$
  • D
    $2\left(F_1+F_2\right)$

Solution

If we take clockwise torque $\begin{aligned} \tau & =\tau_{F_1}+\tau_{F_2}+\tau_{F_3} \\ 0 & =F_1 r+F_2 r+F_3 r \\ F_3 & =F_1+F_2 \end{aligned}$

Hence, the correct answer is option: 'A'.

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