The phrase "onward motion" is correct and usable in written English.
You can use it to describe a continued state of progress in a particular direction. For example, "The train gradually slowed its onward motion as it arrived at its station."
"The river's voice changes constantly, often unidentifiable as male or female, an ever-changing force of onward motion, recycling the past into the present.
It stands as a leitmotif for the industry this year, the lavish departures and loaded decampments, nostalgic reveries despite relentless onward motion through changes of scenery, names and temperament.
Onward, Christian soldiers!
However, the propagation of uncertainty from force measurements through to the predicted derivatives and onward into motion performance predictions, is less well defined.
Many of the songs had lyrics about rambling onward, staying in motion regardless of the goal, and for Mr. Lesh, the Dead's legacy means he can keep on moving.
In magnetic liquids, nanoparticles carry out onward and rotary Brownian motion.
Even those who have held that empty space is a nothing (relationists from Leibniz to Mach and onward) have not generally denied motion, proposing instead that motion of a thing is change in the spatial relations between that thing and other things.
Onward, follow me he motions.
Each patient underwent rehabilitation from the sixth week onward, with exercises to increase range of motion and passive, active, and progressive strengthening.
Each time the car slacked its motion over flat Texas, I reflected, the locomotive had to jerk it onward.
Then, having set a groove in motion, he handed it like a spinning plate to the vibraphonist Bill Ware, who obligingly carried it onward.
