Three particles of mass m each are placed at the three corners of an equilateral triangle of side α. Find the work which should be done on this system to increase the sides of the triangle to 2α.

Here, we first find the potential energy of the system when the sides are of length a.

Initial potential energy,


Now, we find the potential energy of the system when the sides are increased to 2a.


Final potential energy,


Now the work done is given by



1