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Dr_Awesome
9/20/2013 12:41pm,
Hey guys. I have another blog post I though might be of interest here.

It covers levers mostly, and discusses the two ways you can use them:
1) Trade in some distance in exchange for more force
-or-
2) Trade in some force in exchange for more distance (which gives more speed)

I included a few examples from eskrima and grappling, but I'd really like to hear if you guys have some better examples of leverage at work.

http://theamazingdoctorawesome.blogspot.com/2013/09/levers-simple-tools-and-free-lunches.html

ChenPengFi
9/20/2013 1:06pm,
Well, you have science words, levers, wedges (ie triangles) and _ng _un.

Is there really anything to add?

Dr_Awesome
9/20/2013 1:37pm,
Well, you have science words, levers, wedges (ie triangles) and _ng _un.

Is there really anything to add?

Ha. Yea, I had to sift through a lot of science words applied... let's say "over-ambitiously" when I put this together.

Dr_Awesome
9/21/2013 8:28am,
I really would like some ideas for a few special examples, so I can sit down and work out the math, though. I was thinking about maybe knife or gun disarms, or something like that, where we can actually quantitatively compare the difference in force you need to apply using brute force vs letting the lever help you out.

ChenPengFi
9/21/2013 11:27am,
The difference between cradling the neck and the back of the head is marked, during a clinch/plum/snap-down.

A quick explanation of how extrapolation of the length works in regards to lever arms/fulcra would be nice; the maths for newbs...

Kinetic energy vs force, since you brought up velocity, might deserve a nod.

Dr_Awesome
9/21/2013 1:14pm,
The difference between cradling the neck and the back of the head is marked, during a clinch/plum/snap-down.

A quick explanation of how extrapolation of the length works in regards to lever arms/fulcra would be nice; the maths for newbs...

Kinetic energy vs force, since you brought up velocity, might deserve a nod.

Oh man, that is a perfect example to dig into further. Simple in concept, you can test it yourself, the numbers are all measurable... Thank you.

As for the kinetic energy vs force thing, I think that is probably the single most common mix-up you see. I made a whole blog post just for that distinction here:

http://theamazingdoctorawesome.blogspot.com/2013/05/energy-momentum-and-your-fists.html

But here's the quick version: Force gives you a change in momentum. It lets you move things around, knock them over, push them back, etc. Energy is more related to your ability to do localized structural damage to something, like break bones, skin, cause bruises, etc.

Usually, when this gets mixed up on tv shows like "fight science", you see them measure the force of impact, and then make some wild comparison to show the kind of structural damage it would do.

A firmly tossed pillow has the same force of impact as a bullet to the head, FYI. It doesn't mean pillows are deadly.

ChenPengFi
9/21/2013 1:30pm,
Ah, i missed that link earlier.


This section:

So the quick rule to levers in fighting is: grab the long end when you want to control your opponent, and grab the short end when you want to hurt him.


has some problems as written.
Controlling hips and posture/base are kind of at opposite ends of this.

Dr_Awesome
9/21/2013 1:31pm,
The difference between cradling the neck and the back of the head is marked, during a clinch/plum/snap-down.

A quick explanation of how extrapolation of the length works in regards to lever arms/fulcra would be nice; the maths for newbs...

Kinetic energy vs force, since you brought up velocity, might deserve a nod.

And here's a little more of the math on the levers:

A lot of coverage on levers breaks them down into class 1, class 2, class 3, etc, all depending on where the fulcrum, load, and applied force are in relation to each other. I don't like that kind of treatment, because I think it distracts from what is really going on at the heart of it all:

You are using a rigid arm rotating around a point to translate your movement from a linear system to a rotational one and then from that rotational system back to new linear system. Force times distance from rotation on the way in must be equal to force times distance on the way out, due to the conservation of energy. That statement is true no matter what kind of lever you have or what you are doing with it.

So whatever you do to change the distance on the way out, the opposite happens to the force (double distance = 1/2 force, etc).

Of course, we talk about force here because the math is just force times distance and that makes it easy. If we want to start talking about energy, it gets complicated very quickly and we have to start asking specific questions about specific examples.

Does that help with the maths?

ChenPengFi
9/21/2013 1:53pm,
So whatever you do to change the distance on the way out, the opposite happens to the force (double distance = 1/2 force, etc).

This is what i was getting at.
it seems you are targeting a layperson audience so keeping it practical might be beneficial.
Something like this (i would have preferred 100 and 10 kg, and 10 units of length...)
http://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Palanca-ejemplo.jpg/800px-Palanca-ejemplo.jpg

and this:
http://curriculum.vexrobotics.com/sites/default/files/8.15.1%20Levers.png


and this:
http://www.dynamicscience.com.au/tester/solutions/hydraulicus/leversdistance2.gif

can go a lot further than text.



Of course, we talk about force here because the math is just force times distance and that makes it easy. If we want to start talking about energy, it gets complicated very quickly and we have to start asking specific questions about specific examples.

My point exactly, and that criticism stands as it is.



Does that help with the maths?

Just giving feedback.

Dr_Awesome
9/21/2013 3:13pm,
This is what i was getting at.
it seems you are targeting a layperson audience so keeping it practical might be beneficial.
Something like this (i would have preferred 100 and 10 kg, and 10 units of length...)
http://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Palanca-ejemplo.jpg/800px-Palanca-ejemplo.jpg

and this:
http://curriculum.vexrobotics.com/sites/default/files/8.15.1%20Levers.png


and this:
http://www.dynamicscience.com.au/tester/solutions/hydraulicus/leversdistance2.gif

can go a lot further than text.




My point exactly, and that criticism stands as it is.




Just giving feedback.

That feedback is very helpful. You're right, visualizing things makes it easier to understand quickly and easily (way more than text), and I should probably lean on stuff like that way more often than I do. Helping me with clarity is probably the best help I could ask for. Thank you.

Nefron
9/21/2013 4:33pm,
The word for lever and joint lock is the same in Serbian.

Keslet
9/22/2013 7:53am,
Usually, when this gets mixed up on tv shows like "fight science", you see them measure the force of impact, and then make some wild comparison to show the kind of structural damage it would do.

^^^This is one of the main reasons I stopped watching shows like that...the premise always sounded interesting enough (a real examination of different techniques and styles with modern tech to evaluate), but then the science would just suck and approach would just suck!

Krijgsman
9/22/2013 9:03am,
There seems like an awful lot of Judo throws (especially trips/footsweeps) that would qualify as lever movements.

jspeedy
9/22/2013 9:25am,
Can we just start a "bs ma science" thread? Some interesting points have been posted here, and that's why this thread is so boring!

I'll star by saying that I'm a nerd,i love reading about science and what not. But, when you start bringing science into martial arts you get a lot of pseudo science bs. More science does not equal fighting ability, so why do so many schools and ads market themselves as the "science of fighting"? It's crap, shows like fight science ignore the fact that multiple trials are needed to prove anything and variables need to be accounted for. I recall one episode where a small kf guy, an athletic tkd, big boxer ect.were all striking a dummy and the force was measured, no account was made for the different size of the individuals.

cereus
9/22/2013 7:51pm,
I dunno if it's the sort of thing you are looking for but you could look at the same force applied in an armbar vs a kneebar since the motions are very similar but the levers are different lengths.

I've actually been wondering about all the BS MA science out there. I was wondering how people here would go about it to make the tests relevant. Personally I'd like to see martial artists attacking simdavers to see what damage is actually done.

Dr_Awesome
9/23/2013 1:13pm,
I dunno if it's the sort of thing you are looking for but you could look at the same force applied in an armbar vs a kneebar since the motions are very similar but the levers are different lengths.

I've actually been wondering about all the BS MA science out there. I was wondering how people here would go about it to make the tests relevant. Personally I'd like to see martial artists attacking simdavers to see what damage is actually done.

Yea, that's an interesting one too.

As for all the bad science, It seems to boil down to four basic things they get wrong over and over... you guys can probably spot more than me, but these bug me the most:
1) comparing different individuals to each other like they were all basically the same dude
2) confusing force(or momentum) with energy and making wild comparisons
3) taking a tiny sample of data (two punches or something) and/or just taking the best single data point
4) ignoring the whole "fight" part, where you're trying to punch a dude who doesn't want to get punched, instead of a bag or a force plate.

If someone wanted to do an impact test right, they would need to monitor a lot of damned punches (or kicks or whatever) for each individual, and they would need three separate distributions for every individual/strike studied: momentum transfer, energy transfer, and surface area. They would also want to make sure the target used is actually representative of a dude on two feet with some hard parts and some squishy parts who doesn't like getting punched.

Then, if you did that part right, you could separately run some damage tests and map out what energy/momentum/surface area combinations lead to what types of physical damage on the body.

Put the distributions on top of the maps and you have a full picture of what a punch can do. There's probably more details to be included/considered, but that would be how I would design the test.

I would love to get the funding to do a study like that, but until I can figure that piece out, I'll just have to dream about it.