**Example:**3 identical bodies of mass $m$ are at the corners of an equilateral triangle of side $L$. What is the amount of work done in moving them such that the side of the equilateral triangle becomes doubled?

**Solution:**

Initial potential energy, $U_{i}=L−3Gm_{2} $

Final potential energy, $U_{f}=−2L3Gm_{2} $

Work done, $W=U_{f}−U_{i}=−2L3Gm_{2} −(−L3Gm_{2} )=2L3Gm_{2} $