A uniform rod of length $L$ and mass $M$ is pivoted at the centre. Its two ends are attached to two springs…

A uniform rod of length $L$ and mass $M$ is pivoted at the centre. Its two ends are attached to two springs of equal spring constants $k$. The springs are fixed to rigid supports as shown in the figure, and rod is free to oscillate in the horizontal plane. The rod is gently pushed through a small angle $\theta$ in one direction and released. The frequency of oscillation is
  1. $\frac{1}{2 \pi} \sqrt{\frac{2 k}{M}}$
  2. $\frac{1}{2 \pi} \sqrt{\frac{k}{M}}$
  3. $\frac{1}{2 \pi} \sqrt{\frac{6 k}{M}}$
  4. $\frac{1}{2 \pi} \sqrt{\frac{24 k}{M}}$

Solution


$ \begin{aligned} & \text { Restoring torque }=-(2 k x) \cdot \frac{L}{2} \\ & \qquad \alpha=-\frac{k L(L / 2 \theta)}{I}=-\left[\frac{k L^2 / 2}{M L^2 / 12}\right] \cdot \theta \end{aligned} $ $ \begin{aligned} & =-\left(\frac{6 k}{M}\right) \theta \\ \therefore \quad f & =\frac{1}{2 \pi} \sqrt{\left|\frac{\alpha}{\theta}\right|}=\frac{1}{2 \pi} \sqrt{\frac{6 k}{M}} \end{aligned} $

Asked in: JEE Advanced 2009 (Paper 2)

Practice more Oscillations questions on Aicharya