Two masses m and m/2 are connected at the two ends of a massless rigid rod of length l. The rod is suspended by a thin wire of torsional constant k…

Two masses m and $\displaystyle \frac{\mathrm{m}}{2}$ are connected at the two ends of a massless rigid rod of length $\displaystyle l$. The rod is suspended by a thin wire of torsional constant $\displaystyle k$ at the centre of mass of the rod-mass system(see figure). Because of torsional constant $\displaystyle k$, the restoring torque is $\displaystyle \tau=k \theta$ for angular displacement $\displaystyle \theta$. If the rod is rotated by $\displaystyle \theta_0$ and released, the tension in it when it passes through its mean position will be :