A vibratory system consists of mass $m$, a vertical spring of stiffness $2k$ and a horizontal spring of stiffness $k$. The end $A$ of the horizontal spring is given a horizontal motion $x_A = a \sin \omega t$. The other end of the spring is connected to an inextensible rope that passes over two massless pulleys as shown.
Assume $m = 10 kg$, $k = 1.5$ kN/m, and neglect friction.
The magnitude of critical driving frequency for which the oscillations of mass $m$ tend to become excessively large is _____ rad/s (answer in integer).
![GATE ME 2024 Theory of Machines - Vibrations Question 6 English](https://app-content.cdn.examgoal.net/fly/@width/image/6y3zli1lx72qtvm/344f0fe8-4fa7-4f37-b0aa-a0dd0cc0372a/fa624a20-261c-11ef-a279-4f9760cfcb83/file-6y3zli1lx72qtvn.png?format=png)
A spring mass damper system (mass m, stiffness k, and damping coefficient c) excited by a force F(t) = B sin ωt, where B, ω and t are the amplitude, frequency and time, respectively, is shown in the figure. Four different responses of the system (marked as (i) to (iv)) are shown just to the right of the system figure. In the figures of the responses, A is the amplitude of response shown in red color and the dashed lines indicate its envelope. The responses represent only the qualitative trend and those are not drawn to any specific scale.
![GATE ME 2022 Set 2 Theory of Machines - Vibrations Question 2 English](https://app-content.cdn.examgoal.net/fly/@width/image/jaoe38c1m087nrnq/4c86b869-5793-467f-9064-64f196e024e2/a1ac9660-6221-11ef-ad9a-5dfeb0493e4e/file-jaoe38c1m087nrnr.webp?format=webp)
Four different parameter and forcing conditions are mentioned below.
(P) c > 0 and $ω=\sqrt{k/m}$
(Q) c < 0 and ω ≠ 0
(R) c = 0 and $\omega=\sqrt{k/m}$
(S) c = 0 and $\omega \cong\sqrt{k/m}$
Which one of the following options gives correct match (indicated by arrow →) of the parameter and forcing conditions to the responses?