Thick solid line, trajectory of a point moving out from the center of the AGN at which the break frequency has lowered to 1 GHz; thin solidline, the trajectory of one hotspot advancing away from the AGN; dashed line, the trajectory of the midpoint of the arm of a source (see text for more details). Trajectories are shown for a source whose jets each carry total kinetic energy Q₀ = 10⁴⁰ W (top) and Q₀ = 5 × 10³⁷ W (bottom). The value of φ was taken to be 5.