Q 11-06-187JEE MainJEE Main 2020 (2 Sep, Shift 1)Easy
Shown in the figure is a rigid and uniform one metre long rod $AB$ held in horizontal position by two strings tied to its ends and attached to the ceiling. The rod is of mass $m$ and has another weight of mass $2m$ hung at a distance of $75\ \text{cm}$ from $A$. The tension in the string at $A$ is:
Answer: (D) $1\,mg$
Take torques about $B$ (length of rod $= 1$ m). The rod's weight acts at $0.5$ m from $B$ and the $2m$ load at $0.25$ m from $B$:
$$T_A \times 1 = mg\times0.5 + 2mg\times0.25 = mg$$
So $T_A = mg$.
Solution by Sreeraj P, M.Sc Physics