A mass \(M\) is attached to a spring system as shown in the figure. If the mass is displaced from its equilibrium position and then released, what is the time period of its oscillation?
1.
\(2\pi \sqrt{\dfrac{M}{k}} \)
2.
\(2\pi \sqrt{\dfrac{M}{2k}} \)
3.
\(2\pi \sqrt{\dfrac{M}{4k}} \)
4.
\(2\pi \sqrt{\dfrac{2M}{3k}} \)
Hint:\(F=-kx\) Step 1: Find the tension in the lower string. \(\dfrac{T}{2}=k(2x)\) \(\Rightarrow T=4kx\) Step 2: Find the angular frequency of spring-mass system. \(ma=-4kx\) \(\Rightarrow a=-\dfrac{4kx}{m}\) \(\Rightarrow -\omega^2x=-\dfrac{4kx}{m}\) \(\Rightarrow \omega=\sqrt{\dfrac{4k}{m}} \) Step 3: Find the time period of spring-mass system. \(\omega=\dfrac{2\pi }{T}\) \(\Rightarrow \sqrt{\dfrac{4k}{M}}=\dfrac{2\pi}{T}\) \(\Rightarrow T=2\pi \sqrt{\dfrac{M}{4k}} \)
Hence, option (3) is the correct answer.