One system consists of two like charges (q1 and q2) separated by a distance r. a second system consists of two charges that are oppositely charged but that have the same magnitudes as q1 and q2, and they also separated by a distance r. compare the electric potential energy of the two systems

fyt as per the question the magnitude of two like charges are given as q1 and q2.the separation distance is given as r unit.hence the potential energy is given as-

here the potential energy is positive which means the force between  two charges is repulsive.the potential energy is maximum which indirectly denotes that the system is unstable.due to this repulsion the smaller charge may accelerate.

coming to the same charges of opposite nature i.e unlike charges-here the magnitude of charges are same and separation distance is also are,so the potential energy will be given as-

here the potential  energy is negative .so the system of two charges are attracted by each other.

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.