cxz7410 Posted February 24, 2017 Report Share Posted February 24, 2017 Determine the natural frequency in Hz of the system sketched below given the following values:Mass m=4kg Spring stiffness k=28kN/m Length a=121mm Length b=93mm I know thatω=(k/m)^0.5so probably I need to find mshould I write m=4*9.81*(0.93+1.21)? Quote Link to comment Share on other sites More sharing options...
OceanBreeze Posted February 25, 2017 Report Share Posted February 25, 2017 From electrical theory, the resonant frequency = 1/2π√LC The mechanical equivalent is 1/2π√k/Meff You need to first find the effective mass of the system. I don’t think your approach at that is right. The effective mass can be quite complicated and you may need to use a Lagrangian.I am not entirely sure of the correct method but if I have the time I may look into it as I enjoy these types of problems. You might have a look here for some inspiration, particularly the last part on the inverted pendulum with an oscillatory base. Out of curiosity, is this an academic exercise or a practical exercise? In other words, does that design have some practical application as perhaps in seismology? Quote Link to comment Share on other sites More sharing options...
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