Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby KEND on Fri Dec 16, 2011 11:08 am

The shock wave is produced in the body, it is transmitted into a persons body and the energy dissipated there, there is no ground required, it is not being reflected or powered by legs or buttocks, some residual energy from say 'expanding power' may end up at interface of chair and body but that is not the prime mover. As I said before there are many methods of producing the shock wave and the one mentioned inTCC, from ground-thru spine etc is just one of them
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby everything on Tue Dec 20, 2011 9:10 pm

You are "borrowing" from the earth's mass and gravity. Suppose you are an astronaut fighting in space. What then?
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby liokault on Wed Dec 28, 2011 8:52 am

everything wrote:You are "borrowing" from the earth's mass and gravity. Suppose you are an astronaut fighting in space. What then?


You are not borrowing from the earth’s mass or gravity.

If you are an astronaut, you move backwards with as much force as you apply forwards. This is the same as on earth, except on earth, your joints move and absorb the force, meaning that you don’t float slowly backwards.

By your rational, anyone shooting a gun would themselves take the damage of a bullet in the hand every time they pulled the trigger, the principle is the same.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Wed Dec 28, 2011 8:01 pm

that's not entirely true. your joints do absorb some of the energy as friction/heat, but the majority of the energy and momentum is still sunk into the earth.

with your gun example, every bit of the force you exert with your muscles to cushion the reaction force from the bullet's release, also sends that same force into the earth. You will of course spread the energy out due to the mass of your body being accelerated by the force from the gun, but at the end of it all, the reason why your feet don't move when you fire a gun, is because the earth absorbed all that energy/momentum back into itself.

The earth's mass is 5.9736 x 10^24 kg
let's say a human body + the mass of the gun itself is 100 kg for easier math.
A .44 magnum's bullet's mass is about ~16-22 grams, going at about 400-475 m/s.

That means the bullet has a forward momentum of about 10 kg*m/s at most.
That means that in space, your body's momentum would changed to create a difference in velocity of about 0.1 m/s for every bullet you fire. That's about 4 inches/sec. That's really not much momentum. The reason why the bullet does damage is because the force is focused down to a small point, whereas the gun spreads the force along the area of the grip into your palm.
That would change the earth's velocity by about 10^-23 m/s, which is very very very very very very very very very very very (ie, very^20 or so) close to zero. Expanded out, that would be 0.0000000000000000000001 m/s. Which you can't even measure with the best micrometer in the world if you somehow had a fixed point in space to measure against.

This is simple conservation of momentum. Unless you are airborne (which some of the examples that people have given here are), you are pushing off the earth somehow to generate power. While yes, you can generate some power by twisting your waist/hip in mid air, still most power is generated by pushing off the ground somehow. Even if you just twist your waist/hip in place, you are usually still using your legs to turn your hip to generate power, so your feet will likely be pushing off the earth to generate twisting power.

-Fong
Last edited by nianfong on Thu Dec 29, 2011 12:40 am, edited 2 times in total.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Thu Dec 29, 2011 12:53 am

Let's correct your statement in-line:
liokault wrote:If you are an astronaut, you move backwards with as much force as you apply forwards.

This is true, by Newton's third law. However there should be clarification here. Force = mass * acceleration. The gun (which in our case is taken as "part of" the human body) exerts a force on the bullet via the controlled explosion of gunpowder. The force exerted on the bullet creates a change in momentum from 0 to +10 kg*m/s (forward momentum). That same change in momentum (remember, Force = a change in momentum), is then exerted on the human body via the gun grip. As stated previously, assuming a body+gun mass of 100kg, this means, the human body will experience the same change in momentum backward (-10 kg*m/s). If you shot that gun on a frictionless surface (eg you are sitting on a sled floating on an enormous air hockey table), you would then be moving backwards at 0.1m/s.

The only reason why you do not move backwards is because of friction between you and the earth, and the muscles in your body maintaining your frame, and transmitting the force from the gun to your feet. If you somehow let your legs and abs go limp when you shot the gun, you would fall over backwards.

This is the same as on earth, except on earth, your joints move and absorb the force, meaning that you don’t float slowly backwards.

This is partially true. your muscles push back at the force to maintain a frame, and allow the force to be transmitted into the ground via friction. If there were no friction, you would float slowly backwards.
Your joints themselves to not "absorb" the energy, although you may feel like you do. Your joints do absorb SOME of the energy, but again, only a slight amount to heat in your joint lubrication.

By your rational, anyone shooting a gun would themselves take the damage of a bullet in the hand every time they pulled the trigger, the principle is the same.

This is untrue, like I said before. The force exerted on gun by the explosion is spread throughout the gun grip. On the bullet, the same force is focused onto a single point, be your bullet a ball or a typical conic type shape.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby yusuf on Thu Dec 29, 2011 6:20 am

ground connection is not the only way to generate internal power, especially if we consider the body as an elastic bbag filled with water
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Thu Dec 29, 2011 11:58 am

it is not the only way, but it is the predominant way for most power.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby yeniseri on Sat Dec 31, 2011 12:03 pm

My view is totally different but I tend to see this in terms of the following:
a. Stability
b. Neuromuscular entrainment
c. Power generation
d. 'Core homeostasis'
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby Peacedog on Sat Jan 14, 2012 7:53 am

True about not needing to be connected to the ground.

I once watched one of my teachers blast a guy across the room while sitting cross-legged on a table. She transferred the force into the other guy via a pen, as in a writting instrument, held in one hand. Later on we had to take him to the hospital for liver pain.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby nianfong on Tue Jan 17, 2012 12:39 pm

if she didn't also fly across the room in the other direction, she transferred the energy/momentum into the ground while sitting.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby kreese on Mon Feb 20, 2012 7:36 pm

everything wrote:You are "borrowing" from the earth's mass and gravity. Suppose you are an astronaut fighting in space. What then?


I grab you before I hit you, so that it doesn't matter.

The moment your concept of IMA makes you lose your common sense, you are just doing "I", and have lost the "MA".
Last edited by kreese on Mon Feb 20, 2012 8:09 pm, edited 1 time in total.
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Re: Martial Arts Physics 101: Ch 1, Terms and Newton's Laws

Postby Pipefighter,PhD on Wed Jul 16, 2014 6:54 pm

Wow, what a great thread. Nice grasp of hands on physics, Fong!
I know it's an old thread and I'm a new comer, i missed the discussion, but read it all. I want to contribute, even if late.

Vector's are real things, not simply conceptual lines on paper. If I wanted to lift a stone straight up and there was nothing above it, but two trees 40 feet apart, i would take a rope and put it over a branch on each tree and have two people pulling straight down on the ropes evenly enough to lift the stone straight up. The force the rock is exerting is straight up, since that is its only direction of acceleration. The ropes are pulling in one direction, each. But together they form a vector.
Same concept with how a ship sails, creating a vector between the direction of wind and shape of the hull and its resistance to the elastic body of water its in. Total real world vector.
So is grabbing behind the head and throwing an elbow. Vector problem. Very complex vector problem, but if it weren't for awareness of vectors we would never figure out the complexity. It would just get lumped together and labeled with mumbo jumbo.

Also, graham had a really good point about spinal torque. It isn't the ground that is exerting force when your airborne. It's torque based off inertia. The same concept is what enables a cat or a squirrel to flip over in mid air. It uses its muscles in its tail to exert torsional force against its own rigid body. The inertia of its body acts against its tail as resistance and its body turns a bit as its tail flips round and round. I suppose thats how you would punch somebody in outer space, if you were an angry astronaut.
Cool thread. ;D
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