Hello, everyone. So the question came up recently about how Newtonian force should be handled in relationship with magic resistance.
If a magus enchants his fists with magic, so that they are resisted by magic resistance, what happens to that magus' fist when he punches another magus? Will the first magus risk injuring his hand as if he had punched a stone wall?
If the hand is not injured, then that implies that magic resistance violates Newton's third law of motion by cancelling out the force of the punch, and thus brings us the next hypothetical situation. If a maga is falling at terminal velocity high in the air, would enchanting the ground beneath her with a thin layer of magic prevent falling damage due to the now nullified force of the impact?
First, Newton doesn't come along for quite a while. Physics isn't Newtonian in Mythic Europe.
Whether the hand stops abruptly or not, you have the same change in momentum. If you have a 3rd law violation, you have it either way. So I'm not sure why you're looking at the hand being injured as an identifier there.
Consider this from the core book:
If the maga falls onto a magical bridge, she is stopped by the bridge, and takes falling damage.
While I knew Newtonian physics aren't a thing here, I was just referencing it since I'm less familiar with Aristotelian physics. However, it sounds like unlike Newtonian physics, in which it doesn't matter which object is at rest and which is in motion when collision happens, with Ars Magica and magic resistance it sounds like the object in motion is the one that will sustain the damage of abrupt deceleration.
that is not what is being said at all
what is being said is that a magus 1) will not fall through a magical bridge and 2) will take falling damage from hitting one, given that the power comes from gravity, not magic. It is the nature of the motive energy that matters, not what is in motion. If a magically propelled boulder is thrown at the magus, the magus takes no damage. if a catapult is fired at the magus, the magus takes damage. If the magus is fired by magic at a castle, no damage to the magus (actually they won't even be moved by the magic) if the magus is thrown by catapult at a castle, even an enchanted castle, the magus will take damage.
• If the maga falls onto a magical bridge, she is stopped by the bridge, and takes falling damage.
• If the magical bridge falls onto the maga, it is stopped, but does her no damage.
@silveroak That's not what I gathered from the above quote in ArM5. In both of the quoted cases, the source of the motion is pure gravity, with no magic providing any force behind either of them. The only functional difference in the above examples is which object - maga or bridge - is the one in motion.
There is also, if you will, the logical conclusion of what would happen if the bridge did not exist.
Namely that if the magus is falling, they would hit the ground and be hurt, while if the bridge id falling and ceased to exist, the magus would be fine.
However everyone agrees that parma is flawed as a rule, just not as flawed as any other proposed alternative, and at least serves as a starting point for house rules.
And then there is this to confuse the issue with motion and impacts:
If a maga falls into a pit full of magical spikes, she either slides around the spikes if there is room, or finishes lying on top of them if there is not. She takes normal falling damage, but no damage from the spikes.