Power generation

[AngelaG]

mrprecision said:

angelag said:

Dropping your bodyweight increases your mass if you want to hit down (Kibadachi). To hit into with more

Noooooooooooooooooooooooooooo.

It doesn't. Your mass is absolutely fixed. Falling, jumping, flying, running your mass is constant unless you get really frightened. You have to take a meat cleaver to body parts to reduce it or eat loads of food to increase it. What changes is the inertia and energy involved, by dropping your mass down you're getting a helping hand from gravity but your mass stays exactly as it was. (Your weight decreases when you fall, but your mass stays the same).

Yes - we'd already established the difference between weight and mass.

[AngelaG]

mrprecision said:

angelag said:

BTW, about collapsing wrists. The Shito-ryu guys seem to have solved that one. Try punching with your wrist rotated 90° rather than fully rotated 180°. It isn't that different from shotokan, the impact range being about 75%-80% of full extention they just don't turn it quite as much. I haven't figured out why it makes a difference but it does seem to.

You mean exactly like you would in shotokan? The twist comes at the extention of the punch - the impact comes way before that... when your fist would be vertical. You are making the mistake of thinking about it in terms of kumite, rather than in terms of sensible application...

Newton's third law, the same one that sends rockets into space. Then we get into force applied over a surface area... Did you know that when worn, stiletto heels apply bigger forces to the floor than a fully grown elephant would?

Yes I do. I did go to school you know.

Also, sorry but I totally disagree with your assessment of kime. There is no need for extra tension when punching. Enough to stop ourselves from collapsing into jelly, but there is no need to suddenly apply extra tension on impact.

[AngelaG]

Nooooooooooooooooo!! Your mass is fixed. It's fixed I tell you. Sorry, this is probably really annoying, it's the scientific education, it's doing my nut in. . I know what you mean, but it isn't really about changing mass. When your legs are bent, the muscles act like springs and dampers. They damp force coming from a particular direction, the effect is sort of like increasing your mass in that direction, but I hate putting it in those terms. They can turn a short sharp impulse into a long slow one. If the leg's locked it acts like a prop and can transfer the force directly through to the floor, good for pushes(long slow impulse) bad for impacts (short sharp impulse) .

Sorry but your average karateka ain't a physics major. I know that my mass doesn't change (unless I suddenly eat a lot more doughnuts), BUT I am trying to describe what I mean in terms people will understand - not in order to get the Nobel prize for physics. I was trying to point out that direction is just as important as anything else. As we'd established we'd already sorted out that we had been erroneously been using the word mass, instead of weight.

[Mr. Precision]

angelag said:

Sorry but your average karateka ain't a physics major. I know that my mass doesn't change (unless I suddenly eat a lot more doughnuts), BUT I am trying to describe what I mean in terms people will understand - not in order to get the Nobel prize for physics.

Yeah, I know. My excuse is, 4 years of Newtons, Joules, Watts, Pascals, Moles and the rest. Most of it's long forgotten but I still visibly cringe when I hear people talk about power when they mean torque. I usually manage to keep my mouth shut.

[random]

Applying physical, in fact any one the physical sciences to MA is subjective and equally objective. One must fully understand physics, no evidence found, biomechanics, no evidence found, chemistry, no evidence found. I think it is important to forgive misuse of words, and actually look at what someone is actually trying to say; otherwise we end up with pseudo-intellectual sparring, that, because of the nature of experiment can never be proven or applied.

It is like typing with a thesaurus, or even a web page as a reference, we can all do it, and it proves nothing. (Here I really am being mischievous) The OED and the ERD give interesting and somewhat contradictory explanations of some of the theories presented, lets try to keep it simple and intelligible for all to read enjoy and participate, and is that not the true skill, in making it possible for everybody to understand what we type, even if we may have made mistake whilst typing it.

www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/u2l3a.html

This a site which covers all major physical hypotheses, go, be a devil, read it.

[Sionnagh]

One function of kime is to brake when striking into air. Often how tension is applied in a strike varies depending on the target or what is being struck.

The collapsing of the wrist (or not) depending on the amount of rotation is largely influenced by the amount of twist through the forearm of the radius and ulna. With a vertical fist they are pretty much parallel down the length of the forearm but as you rotate into a horizontal fist the bones also twist..


Mick

[Aefibird]

random, can I show my ignorance (yet again!) and ask what the ERD is?
I know what OED is but can't for the life of me think about what ERD stands for.

[random]

There is an important disclaimer in the post with the ERD, I was being mischievous, ;D ;D

[Aefibird]

....right....

[AngelaG]

Bump from the past.

F=MA

Force = Mass x acceleration... So the force of my punch is dependent on a large mass hitting at a high acceleration. Mass cannot be altered, but we can choose which direction our mass is going to travel in, and as both force and acceleration are vectors this would make sense. So accelerating at 20(m/s)/s but in a downwards direction would be no use for punching a person straight in front of you (obvious, right?).

Acceleration is the change in velocity in a unit time. But what if an object is going at a constant high speed? Imagine a fist travelling over a potentially infinite distance and that over time the person manages to hit a speed of 100mph. The mass remains constant, but at that point there is an effective accelaration of 0(m/s)/s. According to f=ma this means that there would be no force if it was to then strike an object as anything multiplied by 0 is 0. Furthermore looking at Impulse = force x time then impulse etc. would also be 0 as force is 0, regardless of time taken...

However surely if an object with a large mass strikes another object at 100mph, then there will be damage done. If a car was to hit me whilst maintaining a constant high speed then there will still be a lot of damage done to my body...

Is there more here than meets the eye, as F=MA is the equation often used by martial artists to explain the physics behind striking.

[Andy]

OMG.
'Physics' x 'MA discussion' = 'does this still go on'?

[AngelaG]

Sure! It's easy to get bogged down in too much physics, but up to a point I believe it is useful! For example, knowing about the different types of levers and how they work - I think this is very useful when applying locks/bars etc.

[death]

[quote from Mr.Precision
I did hear an interesting point from the shito-ryu sensei about punching. They punch and pull back very quickly, he described it as dropping a stone in a pond and allowing the ripples to spread. Now, I was sceptical at first but it does have some scientific merit.... When you hit something elastic you get a shock wave, called an impulse, the impulse travels through the object till it reaches the other side and then reflects back.

The damage from an impulse is caused by very high pressures on the front of the wave compressing the media it's traveling through and very low pressures at the back of the wave pulling the material apart. This is BTW how nuclear weapons can do so much damage, the overpressure at the front of the shock wave is unbelievably large and the wave is very short.

If you continue pushing the punch the overpressure at the front of the wave exists but the underpressure at the back of the shock wave is damped out by your fist. That's the theory anyway. increase the impulse and reduce the damping by punching quickly and pulling the hand back after. I'm not completely convinced, I'd have to see some experiments in a lab with someone punching something elastic like a bag of water or a gelatin block.
[/quote]


Mr Precision;
This might convince you that it is not just a theory.(maybe)The reality is in punching the makiwara.A proper
makiwara,pole in the ground or floor mounted,with some flexibility.There are two ways of hitting the makiwara.Hit and stick,and the snap punch.The hit and stick method is the way most people train on it.And it is the starting method.You hit the board and push.In the snap punch you hit it really fast,and deep.Then with draw the fist even faster.The way you can judge the penetration is to hang a string with a weight on it about 6 to 8 in.behind the board.(depending on how flexible it is)Hit the board with a push punch.Move the string back until you can't hit it with the board.Now hit it with snap punches and see how much farther you have to move the string back. And why does this work?Because of what you said up above?(maybe)
Couple of more examples.Kicking a heavy bag;if the bag swings you have used hit and stick(push).If the bag wraps around your foot and doesn't go any wear ,you have used a snap kick(speed).Another wonderful experiment is to hit a body.Hit and stick, the body will fly back wards.With snap punching technology,the body will fall straight down in a pile,and will have massive internal damage.
I may be wrong,I have been before.