Question

Two blocks of mass 3 kg and 4 kg hang from the ends of a massless rod marked in seven equal parts.
Find out at which of the points indicated should a string of mass suspended so that whole system remain in equilibrium?

• A. A
• B. B
• C. C
• D. D
• E. E

Answer 1

The correct option is B B

For the system to remain in equilibrium, the torque about the point of suspension must be zero.

Let the distance of point of suspension from $4kg$ block be $x$.

Then under equilirium,

$4\times g\times x=3\times g\times (l-x)$

$⟹l-x=\frac{4}{3}x$

$⟹x=\frac{3}{7}l$

Hence the point of suspension is point B.