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Message: <blockquote data-quote="kigmatzomat" data-source="post: 8722311" data-attributes="member: 9254">I posted at 1am local time on a gaming board from a phone to comment on why E=Mc^2 was completely inapplicable to a punch (A fact that got lost in an edit and was added in a follow up) while having a BAC of "happy glow". Not really going to be concerned about failing to fully describe a term given that the "punch" in question could come from an 18" pixie or a tentacled otyugh.So first off, F=M*a.  Work (energy)= F*d.  Ergo W=M*a*d.  Both have units of kg*m^2/s^2.  You probably got hung up in named units. I always decompile joules, newtons and such to fundamental units as quickly as possible. Makes it easier to find which components of a formula will be irrelevant at the scale in question so I can ignore it sooner.I am a licensed engineer.  If I need to deal with a collision, the energy to turn a human body into a 50m smear isn't even a round off error on the last significant digit. Not something I have had to do in the last 20 years, though, as I am a retired engineer.Overall this is normally a "spherical cow" scenario, where tons of hand waiving is applied. Although engineering doesn't like to say it uses "assumptions" like those ivory tower academic physicists, we call them statistically significant multipliers for safety factors. Same diff.  (You would be stunned at the amazing oversimplifications done as part of engineering best practices that let us reduce a ginormous physics problem to a simple 2-term approximation. We get away with it because they are based on empirical test results within the energy/mass tier in question, always errs on the conservative (safe) side, and then we add another large (~40%) safety factor. As long as you choose the right "tier", its easy peasy. That transition between tiers? Ugh, we hate that. Sometimes there are differential equations to solve and they're the worst.)If you are throwing a punch, the best case scenario is already  gone, its now all shades of bad. First shade of bad is terrain. Ever gotten in a fight in mud or on loose gravel? Yeah, totally not a pinned connection to the ground.As to the terms I didn't define, M' is the "limb mass", as punch style will change that. Could be as small as the arm below the elbow a quick snap punch, arm+ fraction of shoulder, +component of torso on a roundhouse, etc. Add tentacles and such and its all messy.Total mass is relevant. From my minimal martial arts experience decades ago, it is much easier to break a board starting at walking speed than while keeping the center of mass essentially stationary. If two fighters move towards each other, the collision forces can increase significantly. Or I can just point at head on collision energies between cars if you want something less anecdotal.I did make a nod towards the time of collision, though I referred to it indirectly through assumptions of the incompressibility of fluids.And did you actually try to say flying is irrelevant in a gaming concept? In d&d it becomes available at 5th level and magic items can make it show up at 1st even for humanoids.  That ignores flying opponents, like the aforementioned pixie.So ultimately, this was all a flying incompressible spherical cow used to explain why the cow is not spontaneously converting its mass into a planet-shattering explosion.</blockquote>

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