Question

A rod OA of mass $4kg$ is held in horizontal position by a massless string AB as shown in figure. Length of the rod is $2m$. Find tension in the string.

• A. $\frac{40}{\sqrt{3}}N$
• B. $20N$
• C. $50N$
• D. $62N$

Answer 1

Answer: (A)

$\frac{40}{\sqrt{3}}N$

As the rod is in equilibrium, thus net torque about point O is zero i.e. ${\tau }_o=0$

$\therefore$ $\left(Tsin{60}^o\right)2-mg\left(1\right)=0$

$⟹$ $T=\frac{mg\left(1\right)}{2\times sin{60}^o}=\frac{4\times 10\times 1}{2\times \frac{\sqrt{3}}{2}}=\frac{40}{\sqrt{3}}$ $N$