• # question_answer A uniform cable of mass 'M' and length 'L' is placed on a horizontal surface such that its ${{\left( \frac{1}{n} \right)}^{th}}$part is hanging below the edge of the surface. To lift the hanging part of the cable up to the surface, the work done should be :             [JEE Main 9-4-2019 Morning] A) $\frac{MgL}{{{n}^{2}}}$             B) $\frac{MgL}{2{{n}^{2}}}$C) $\frac{2MgL}{{{n}^{2}}}$                       D) $nMgL$

Mass of the hanging part $=\frac{M}{n}$             ${{h}_{COM}}=\frac{L}{2n}$ work done $W=mg{{h}_{COM}}=\left( \frac{M}{n} \right)g\left( \frac{L}{2n} \right)=\frac{MgL}{2{{n}^{2}}}$ Option [b]