dchudz

Oversleep-- I don't think "momentum is conserved" works, due to some of the examples above. For example (quoted by ulyssessword above as from HoA ch. 78 pp 678): If momentum were conserved, growing heavier wouldn't add momentum to the blow (and would in fact decrease kinetic energy). I'm now thinking that maybe the conserved quantity is kinetic energy. Then increasing your mass does add momentum to the blow. If m1 and v1 are the original mass and speed, and m2 and v2 are the new mass and speed (after changing mass), m1*v1^2 = m2*v2^2 so v2 = sqrt(m1/m2)*v1. Then momentum (mv) is increased when increasing mass. This looks to me like it explains everything that happens when changing mass reasonably well. Decreasing mass to slow down while falling looks like an exception, but (as some folks discussed above) air resistance explains that: it's plausible you'd slow down after initially speeding up a lot. (It's a bit odd that the text doesn't mention the initial speeding-up, though. I guess maybe people don't notice it, since they're already speeding up from the fall?) [Edit: As someone mentioned above, "which reference frame?" is still a problem / open question.]

Exactly. The world-building is a lot of what's interesting about fantasy, "how does this magical system work?" is the most important part of that here.

There's lots of textual evidence above that your velocity is preserved (not momentum) when using a metalmind to change mass. But then in Shadows of Self, Ch 24, there's this: This seems to suggest something like momentum is conserved, and seems inconsistent with quotes people have above where nothing like this happens. What's going on? Is it possible to resolve the inconsistency?