Question
An automotive engine having a mass of 135 kg is supported on 4 springs with linear characteristics. Each of the 2 front springs have stiffness of 3 MN/m while the stiffness of each of 2 rear springs is 4.5 MN/m. The engine speed (RPM) at which resonance is likely to occur is
The correct answer is
104/(π)
The springs act in parallel: \(k_{eq}=2(3\times10^6)+2(4.5\times10^6)=15\times10^6\ \mathrm{N/m}\). Therefore \(\omega_n=\sqrt{k_{eq}/m}=1000/3\ \mathrm{rad/s}\). For one excitation cycle per revolution, \(N=\frac{60\omega_n}{2\pi}=\frac{10^4}{\pi}\ \mathrm{rpm}\).
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Important Questions from Equivalent Stiffness
The resistance of a material to elastic deformation is called _______.
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