Do stop thrusts end movement?

[Tomsdad]

Originally Posted by aesir23

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Knock back in GURPS generally makes much more sense if you picture it as "opponent had to take a step backwards or lose their balance" rather than "opponent flies back entirely from the force of the blow."

Part of the problem is it would take much more energy to knock back an opponent who's moving forward than one who's standing still (you have to overcome their forward momentum rather than just tipping their balance back.)

Yep exactly

Originally Posted by aesir23

It would make sense to me to say that each hex of knockback merely cancels out one movement point, except that GURPS doesn't alway distinguish between the states "opponent moved last turn but has stopped on his current hex" and "opponent is still moving, but he doesn't have any more movement points to spend until his next turn.

Yep, I think you can fudge it somewhat though

Originally Posted by aesir23

Another problem is Newton's Third Law. If a man is charging me, and I thrust my quarterstaff into him, I may be able to stop him, but I'm also going to be forced backwards.
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Thing is Newtons Third law in abstract doesn't take into account friction, footing and likely braced weapons. i.e the situation is not just two frictionless objects colliding (but yes it will apply at some point if the forces are great enough to overcome all that, as you say above it how you view knock back that's the key)