• # question_answer Two heavy rotating masses are connected by shafts of lengths ${{l}_{1}},{{l}_{2}}$ and ${{l}_{3}}$ and the   corresponding diameters are ${{d}_{1}},{{d}_{2}}$ and ${{d}_{3.}}$this system is reduced to a torsionally equivalent system having uniform diameter $''{{d}_{1}}''$ of the shaft. The equivalent length of the shaft is: A) $\frac{{{l}_{1}}+{{l}_{2}}+{{l}_{3}}}{3}$B) ${{l}_{1}}+{{l}_{2}}{{\left( \frac{{{d}_{1}}}{{{d}_{2}}} \right)}^{3}}+{{l}_{3}}{{\left( \frac{{{d}_{1}}}{{{d}_{3}}} \right)}^{3}}$C) ${{l}_{1}}+{{l}_{2}}{{\left( \frac{{{d}_{1}}}{{{d}_{2}}} \right)}^{4}}+{{l}_{3}}{{\left( \frac{{{d}_{1}}}{{{d}_{3}}} \right)}^{4}}$D) ${{l}_{1}}+{{l}_{2}}+{{l}_{3}}$

Equivalent length, ${{l}_{e}}={{l}_{1}}+{{l}_{2}}{{\left( \frac{{{d}_{1}}}{{{d}_{2}}} \right)}^{4}}+{{l}_{3}}{{\left( \frac{{{d}_{1}}}{{{d}_{3}}} \right)}^{4}}$