[Science] The Hard Science of Low Gravity versus High Gravity

[Anthony]

Originally Posted by Fred Brackin

No, you don't lift your feet at all when punching. Normally you set them instead.

I specifically mentioned stepping into a blow to increase its power. If you're not doing that (only using upper body strength), gravity doesn't much matter.

[Fred Brackin]

Originally Posted by Anthony

I specifically mentioned stepping into a blow to increase its power. If you're not doing that (only using upper body strength), gravity doesn't much matter.

You do not throw the punch until both feet are on the ground. You then push backward with both feet trying to transfer that energy into the striking arm. Only wuxia fighters throw attacks in mid-air and they of course are immune to gravity by definition.

Very seriously any rapid forceful motion of the human body is a transaction in inertial mass rather than gravitational weight. An astronaut in microgravity does see his normal walking rate decline towards zero or possibly even become an irrational number but he simply stops trying to walk. His ability to move quickly is largely unimpaired. Do I really need to dig up a link to the Skylab astronaut doing acrobatics?

[Anthony]

Originally Posted by Fred Brackin

You do not throw the punch until both feet are on the ground. You then push backward with both feet trying to transfer that energy into the striking arm.

Right, that's dependent on gravity; without gravity that pushing 'back' turns into hopping into the air, which isn't useful.

[Fred Brackin]

Originally Posted by Anthony

Right, that's dependent on gravity; without gravity that pushing 'back' turns into hopping into the air, which isn't useful.

Are talking about situations with _no_ gravity? I'll admit you can't plant your feet with no gravity but there are obviously intermediate levels of gravity where you can stand. You don't start bouncing up and down as soon as you hit .99G.

You're still doing the bio-mechanics wrong anyway. Any downward push is minor compared to a forward/back component which will push your soles across the ground horizontally.

Really, rapid forceful motions of the human body are about inertial mass and people do not move in slow motion in reduced gravity.

[Anthony]

Originally Posted by Fred Brackin

You're still doing the bio-mechanics wrong anyway. Any downward push is minor compared to a forward/back component which will push your soles across the ground horizontally.

Incorrect. The primary push direction is in the same direction as the extension of your leg, which is going to be more down than sideways unless your leg is at 45 degrees or more.

In general, sideways acceleration is capped at (acceleration of gravity) * horizontal offset of pushing contact point) / (vertical offset of center of gravity); if you try to go faster than that, you jump. At a certain point you start slipping, but this isn't normally a factor for legs.

[Flyndaran]

Would that mean a super strong character punching a wall is going to go flying backwards under earth gravity?

[Anthony]

Originally Posted by Flyndaran

Would that mean a super strong character punching a wall is going to go flying backwards under earth gravity?

Theoretically yes, though it would require an awful lot of super strength.

[Ulzgoroth]

Originally Posted by Flyndaran

Would that mean a super strong character punching a wall is going to go flying backwards under earth gravity?

That's almost trivial - if you push on the wall, the wall pushes on you, and if you push hard enough at least one of you is going to move.

[Bruno]

Originally Posted by Flyndaran

Would that mean a super strong character punching a wall is going to go flying backwards under earth gravity?

Is it a super strong wall and does this person not have an elbow? If they don't have an elbow (or their elbow is super-tough and their autonomic reflexes are broken) then if the wall doesn't give, the person will. If they don't fold at the elbow, and they don't break their bones, then they have to disipate that energy somehow. Movement is a lot more plausible than creating a blast of light and heat, but this is in the context of an unstoppable force meeting an immovable object so *shrug*

EDIT: I mean, that's a short description of how animals with legs walk, run, and jump - doing it at a 90 degree angle doesn't make it privileged in physics.

[Anthony]

Originally Posted by Ulzgoroth

That's almost trivial - if you push on the wall, the wall pushes on you, and if you push hard enough at least one of you is going to move.

Well, the issue is mostly how much force is required to overcome gravity. It actually depends on attack angle, if you uppercut the wall you aren't going anywhere because the reaction is pushing you into the ground.