• # question_answer A shaft has two heavy rotors mounted on it. The transverse natural frequencies, considering each of the rotor separately, are 100 Hz and 200 Hz respectively. The lowest critical speed is: A) 5367 rpm                      B) 6000 rpmC) 9360 rpm                      D) 12000 rpm

$\frac{1}{\omega _{n}^{2}}=\frac{1}{\omega _{1}^{2}}+\frac{1}{\omega _{2}^{2}}$ $\frac{1}{{{100}^{2}}}+\frac{1}{{{200}^{2}}}=\frac{1.25}{{{10}^{4}}}$ ${{\omega }_{n}}=89.433\,\,Hz\,\,or\,\,5367\,\,rpm$