A) \[mgR\]
B) \[\frac{mgR}{6}\]
C) \[\frac{mMgR}{(M+m)}\]
D) \[\frac{mMgR}{6(M+m)}\]
Correct Answer: B
Solution :
If the body of mass m is moved from the surface of earth to a point at distance h above the surface of earth, then change in potential energy or work done against gravity will be \[W=\Delta U=GMm\left[ \frac{1}{{{r}_{1}}}-\frac{1}{{{r}_{2}}} \right]\] Here\[{{r}_{1}}=R+R=2R\]and \[{{r}_{2}}=R+2R=3R\] \[=GmM\left[ \frac{1}{2R}-\frac{1}{3R} \right]\] \[=\frac{GmMR}{6{{R}^{2}}}\] \[=\frac{mgR}{6}\]
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