One question...
What takes priority:
The actual energy value, or "being able to harm characters who can withstand such forces". AKA "being able to harm someone/thing with a specific durability".
If the latter, then I see absolute zero problems with standard humans being 10-A+ or 9-C, as people endure 9-C things all the time?
You know jumping off that one 0.5m ledge? Yeah, that's 10-A+ to 9-C kinetic energy on impact. Standing? Also 9-C potential energy typically.
And yes, I do mean a mere half-meter ledge. Most people would hit the ground with 9-C kinetic energy on impact, and since you'd most likely be completely to a complete halt on concrete...all the energy/force, is going back into your body according to Newton's Third Law. And yet, people are completely fine after that, even children can do that with zero problems; though it would be less KE due to children having lower masses than adults.
When you fall from half a meter though- there are two relevant scenarios to consider force/durability wise.
1. You're standing upright and land feet-first- in which case, your body does not come to a dead halt upon hitting the ground, because upon landing, your knees bend forward and your core to upper body continues to fall downward after your feet stop / hit the ground, decelerating gradually to zero as your legs straighten themselves out again. So you don't take the entire impact at once.
(Go ahead and jump 1.5 feet / 0.5 meters in the air, but keep your knees locked and legs completely straightened pencil-style when you land. Be as rigid as possible- make sure you land heels first, so your toes don't act as a break, and also that your knees do not bend At All when you land.
You'll feel the recoil go straight up your legs, and chances are your core/torso/back will bend or throw itself forward anyway when taking the impact, regardless of how rigid you try to be.)
2. You belly-flop from 0.5 meters above the ground. The impact on your body will be overall less intense due to the greater surface area that it's spread across. Additionally, the body still does not take the whole force at once, only instead of absorbing the shock by [some part bending so the rest of the body decelerates instead of coming to an immediate stop] like before, here the body itself squishes/flattens a bit so every part does not come to an immediate stop. Even then, it'll hurt and you could break your nose. (Ever belly-flop into a pool?)
Also, plenty of people have died from literally just falling over from standing height on to a hard surface.
Then, where does the remaining energy go?
It cannot violate Newton's Third Law, especially since this is an IRL case.
Where...does the remaining 50% go to? As every force has a equal opposing force.
That's what I'm wondering myself.
@Spinosaurus75DinosaurFan @DontTalkDT Help?
Newton's Third Law is not being violated.
The fist doesn't take 50% of its force back, it takes 50% of it's energy. While Momentum must be conserved, Kinetic Energy can go a ton of places if the collision isn't "perfectly elastic."
Explanation:
It actually has little to do with surface area. Human fist is made of relatively soft and weak tissue. So when you land a punch more than 50% of impact energy goes back into your arm.
This issue can be fixed with brass knuckles
(I'd like to add that a lot of that comes from the fist/fingers crumpling, which is where the whole [roll of quarters in the hand] trick is for. Aside from the extra weight, it keeps the fist "solid" by preventing the fingers from crumpling inward during the collision, making a far greater impact.)
