(4) Derive the equivalent spring constant (keq) that relates the vertical displacement of the mass (x) to a vertical force applied to it. If the rigid bar is massless, express the natural frequency of the system. The system is shown in Fig. 1.3. Express both quantities in terms of given parameters (k, k2, a, b, m), assume small angular displacement for the rigid bar, and assume static equilibrium when writing equations. b k m F x k2 a Figure 1.3: Mechanical system to define equivalent spring constant in Problem 4.