QUESTION 3 An un-damped vibrating system excited by a sinusoidal force of constant magnitude but variable frequency has a displacement between extreme positions of 50 mm at 200 rpm and 25 mm at 600 rpm, and it is known that the critical frequency lies somewhere between those two speeds. Calculate: 3.1 the natural frequency of the system in rad/s, and 3.2 for a suspension stiffness of 7 kN/m, the mass of the suspended system 3/6