The Dresden Files > DF Spoilers
(BG Spoilers) LTW Conservation of Speed w/ Mass Shift
Avernite:
Clearly the proper frame of reference is the LtW frame of reference, in which the earth is rapidly approaching LtW. in this frame of reference the mass is just added at zero speed.
morriswalters:
Einstein has officially rolled over in his grave.
Arjan:
--- Quote from: morriswalters on January 02, 2021, 06:19:38 PM ---Einstein has officially rolled over in his grave.
--- End quote ---
Newton. This is all classical mechanics.
KurtinStGeorge:
--- Quote from: BrainFireBob on December 31, 2020, 05:40:11 PM ---Mass doesn't change acceleration at all. Momentum needs to be conserved, though, so unless the new mass is already accelerated to match, the same momentum is distributed over more mass, resulting in a slowdown.
EDIT: If you're interested, the relevant equation is the force of gravitation between two bodies.
F=m1a=G*( m1m2)/d^2
This means the acceleration due to the gravitational force is
a=G*m2/d^2
That's invariant from the frame of reference of m1.
Second edit: It's essentially a 100% nonelastic collision
--- End quote ---
Correct, but Jim's description bothered me as well, because from what I've seen a hawk that dives on its prey still has its wings spread out a bit; by which I mean it's not in a complete freefall. I live in a desert area in Southern Utah and often see hawks making lazy circles in the sky when I go on walks in the morning or if I go on a longer hike in the nearby hills. They drop pretty damn fast when they dive on something, but they don't drop like a rock and I don't believe that they ever reach terminal velocity. They control their speed and angle of decent, something an elephant could never do.
If the hawk turns into a elephant an instant; let's say two feet, before it hits the target that won't change anything of significance. If it happens fifty feet away, then maybe it would. It would take some math skills beyond mine, but I suppose it could be calculated. I think even an experienced shape shifter would be hard pressed to be able to make such a calculation on the fly, or in this case, during the fall.
morriswalters:
--- Quote from: Arjan on January 02, 2021, 06:51:17 PM ---Newton. This is all classical mechanics.
--- End quote ---
No this is magic. Physics need not involve itself. Jim even uses the fact in Cold Days in Harry's fight with Cat Sith on the boat.
--- Quote ---Sith bounced off me, which was what I had hoped would happen. In my line of work, I’ve dealt with more than one critter that is faster than fast. When they’ve got their feet underneath them, it’s the next-best thing to impossible to land anything on them—but when they’re in the air, they’re moving at the speed gravity and air resistance dictate, like everybody else. For that one portion of a second, Sith was an object moving through space, not a blindingly fast killing machine. Someone who didn’t know that wouldn’t have known to be ready for it.
Butcher, Jim. Cold Days (The Dresden Files, Book 14) (p. 439). Penguin Publishing Group. Kindle Edition.
--- End quote ---
It's magic and you can't make it work as anything else.
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