  The model of non-ballistic jet motion proposed in 2008 provides a simple
explanation to the inward jet motion and bent jet. Recently, evidences of such
a non-radial motion increase rapidly, and more complicated morphologies appear.
On the other hand, the ballistic plus precession model likely holds in majority
samples of jet motion. This paper discusses the relationship between the
ballistic and non-ballistic model of jet motion, which suggests that the
interaction of ejectors with ambient matter can produce knots at different
stages of evolution and hence different separations to the core. And as a jet
precesses, knots produced between the core and the deceleration radius result
in spiral pattern expected by the model of ballistic plus precession; and knots
generated at the deceleration radius display non-radial motion such as bent jet
or oscillation of ridge-line. This paper develops the first non-ballistic model
in four aspects. Firstly, it provides a numerical simulation to the production
of multi-knot for a precessing jet. Secondly, it fits the precession behavior
of multi-knot and interprets the oscillation of ridge lines like S5 1803+784.
Thirdly, it gives an unified interpretation to the bent jet applicable to both
multi-knot and single knot. And fourthly, the problem of very large numbers of
observed outward motions as opposed to the inward ones is addressed in a new
scope.
