Two balls of masses m1=1 kg and m2=2 kg are attached to a massless rod of length (l=1 m). Two parallel forces having equal magnitude of F=1 N, opposite in direction (couple) are acting on both the balls as shown in the figure. Find the angular acceleration of the system (α) about an axis passing through mid-point of the rod and also perpendicular to the plane of the rod. (Take anti-clockwise rotation as +ve)