But I do want to say one thing. I am sure some will write me off for my "one direction, one magnitude" phrasing. I stand by it, but let me emphasize that in terms of motor commands and application, I would never suggest things like "a groundpath only has one direction of force." To touch a person "with the ground" goes hand in hand with receiving, so yes of course it is a 2-way street.
Imagine a ball suspended in the air (via imaginary antigravity) and you push it with jin. If the ball goe backward, a linear force was applied, fairly undoubtedly. If someone wants to posit that the ball went backward because of the tangential effect of angular momentum caused by "contradictory spirals", I'm happy to listen.