Gaining power from pulling a punch?

[Jeremy_V]

ok I have never taken a physics class in my life but I understand a lot about it from real world application. I am taking a wing chung doe martial arts class and they are saying that its the only form that is based on science however they seem to have some major flaws in there thinking however I don't know how to explain things to them right so here are my questions and please show me how I can prove to them what the answers are.

#1 they say that if you punch a person and only penatrate 2 inchs and recoile (pull your punch back really fast) that you will have a lot more power in your punch becasue of the recoil and that this recoil will cause more damage to the person then if you would have fallowed through with the punch. the reason that they state this is because they say that if you continue to fallow through your mass will be joined with theirs and that your energy will not go into them but rather back into you. another thing they say is that if you fallow through your energy is not obsorbed into the body because they start moving backwards after the hit while with the 2 inch hit they don't move and all the punch energy stays in their body.

so what can I do to prove them wrong? to me it is very simple however a lot of people are believeing what they say and that it is proven fact I believe it is totally fiction, I can't see how taking power away from a punch could in any way deliver more energy into the target.

#2 from this 2 inch punch they say that a shockwave is created that could otherwise not be made if you did not recoile. how do I prove this wrong?

I don't understand all the terms in physics so please explain things in words that avrage americans can understand it in. (The guys I will be explaining it to are not too smart)


I love it when people say that they are the only one who uses sciencs and then they dont.

Thanks for any help
Jeremy

 

[DaveC426913]

so what can I do to prove them wrong?

To what end? I mean, what do you think will be the outcome of this discussion with them?

 

[Jeremy_V]

The reason I want to prove my point to them is because I am studying to be an instructor under them and I don't want to be teaching lies. I want to teach my students the truth and have the form respected because of how it works. anyone that hears them explain these things that understands physics at all will know that they are full of BS. however the masses will believe the lie because of their examples.

They think things work for one reason but in reality its another. so they show an example as to how much more power their punch has by hitting you really fast but only going 1 inch deep then they hit you slow and go 5inchs and say see how much more the 1inch hurt see how much more power you have when you pull your punch back fast. the truth is that its their kinetic energy of the fast punch that had more power then the slow one however if they had punched at the same speed 5inches deep it would have hurt much much more.

I am looking for some kind of example I can show them that any idot can understand because they are brain washed by their master.

 

[DaveC426913]

Right. My point is, how can you expect them to allow you to teach if you don't follow their principles.

You are, of course right - they are full of hogwash - at least, as it has been explained. I would allow for the possibility that it is not the physics that is flawed but the explanation (usually by being dramatically oversimplified i.e. they may be giving you the answer they give any idiot who can't think through the physics). There's an outside possibility that a knowledgeable person can explain it in more detail such that it does follow known laws of physics.

But more likely, it's just hogwash.


Nonetheless, it seems to me that you have three choices here:
- ask for further education in the physics area, either it will be vindicated, or you will find it's hogwash
- suck it up and toe the party line
- say thanks but see you later.

IMO, the one option not open to you is to try to refute them.

 

[Jeremy_V]

Thanks for your advice,
I am quite sure that it is total BS and that they are explaining it right to me because I have asked and questioned them about this before. the founder of the style has explained it to me in person as well. I think that the style is good because the fast recoile puts you back in position for the next move its just that they lie to us and tell you that it gives you more power. the whole system is based on this fast recoil and the power it creates. I am going to make some exparments to prove my point to them and then expect to get kicked out. The only reason I am not just quitting is because some of my friends have been brainwashed by these guys and believe all there BS I want them to know the truth and hopfully they will either quit or get things chaged. We are being trained to open a school so if we all bann togeather then things might get changed but I doubt it. I am not totally sure if the guy who started the system is totally dumb or if he is just using this as a marketing scam pormissing that you will acheve more power then any other way if you use his systme...

thanks again for all your help! I have learned a lot form this sight in the last two days.

Jeremy

 

[DaveC426913]

Thanks for your advice,
I am quite sure that it is total BS and that they are explaining it right to me because I have asked and questioned them about this before. the founder of the style has explained it to me in person as well. I think that the style is good because the fast recoile puts you back in position for the next move

Huh. I had not thought of that but it soind like an excellent tactic. Any outstretched limb makes an excellent target for counter attack, as well as likely putting you off balance.

its just that they lie to us and tell you that it gives you more power. the whole system is based on this fast recoil and the power it creates. I am going to make some exparments to prove my point to them and then expect to get kicked out.

Yeah.
Or they'll ridicule you. Worse, if you attempt a demonstration but don't really back it up convincingly, they may riducule you mercilessly.

The only reason I am not just quitting is because some of my friends have been brainwashed by these guys and believe all there BS I want them to know the truth and hopfully they will either quit or get things chaged. We are being trained to open a school so if we all bann togeather then things might get changed but I doubt it.

Well, good luck.

I am not totally sure if the guy who started the system is totally dumb or if he is just using this as a marketing scam pormissing that you will acheve more power then any other way if you use his systme...

I imagine it is the usual "plausibility" tactic. If you can describe something in a way that sounds right, it's good enough. It doesn't amtter whether it's true or not.

 

[stewartcs]

...the reason that they state this is because they say that if you continue to fallow through your mass will be joined with theirs and that your energy will not go into them but rather back into you. another thing they say is that if you fallow through your energy is not obsorbed into the body because they start moving backwards after the hit while with the 2 inch hit they don't move and all the punch energy stays in their body.

Sounds like they've watched one too many episodes of Kung Fu.

I believe they are confusing the effective force "felt" by an object due to the objects momentum divided by contact time. Remember the old analogy of catching an egg without breaking it? If you allow enough time (by moving your hand away from the egg as it comes into contact with you) to absorb the momentum, the force you "feel" is less. Hence the egg doesn't crack.

The problem with what they're telling you is if you are pulling the punch back, you are negating the force you are applying. So how could the other person feel more force by you reducing the force you're applying??

Like Dave said, it's hogwash.

 

[Jeremy_V]

physics for dummies?

Thanks for the replies! Do any of you happen to have physics for dummies? maybe I can force them to read it oh wait maybe I ment common sense for dummies yea that's the one they need to read.

So I was thinking about using a vat or big bag of water to demonstrate the shock waves created by each kind of strike. Sense the human body is 98% water I thought this would be as good of a demonstration as I can get witout using billistic gel. What do you guys thinK?

Is there any other kind of demonstration I could do to prove my point? I was thinking about just hitting them really hard each way but I don't think they would like the outcome of that very much ha ha.

Thanks again!

 

[sephirothrr]

Well, they may be right about their punch theory. All forces are diluted by the amount of time that they are applied. That's the idea behind bumpers and crumple zones in cars. The longer the force is applied, the less work is done, since work is Force / Time.

I'm not sure about the shock wave part.

 

[Jeremy_V]

sephirothrr,
What you said almost makes sense and I am sure that is how they came up with the idea in the first place but from my understanding it is false.

In your example you are saying that because my full punch takes longer that it has less energy however that is not the case because my punch has exactly the same energy up to the two inch point at that point the time is exactly the same. after they start pulling back I keep driving through adding more energy into there body. does this make sense?

Jeremy

 

[sephirothrr]

Hmm... interesting...
So would that mean that the theory if reducing the impact of car crashes is wrong?
Or perhaps car crashes deal with only an instantaneous force instead of a continued one.

Well, here's the problem. When you punch, you would be applying the same force, but a held-out punch would be for a longer time. While the kinetic energy would increase, the work done would decrease. That part I'm fairly sure about.
However, I did come up with one possible reason - when a body is at rest, it receives the brunt of the force. However, after a prolonged force is applied, the force could then be converted into a horizontal velocity, or in this case, the person would be thrown to the side. That cushioning would weaken the force.
However, you make an excellent point, and I am not so sure anymore.

 

[TopCat]

Just to elaborate on what stewartcs said, the way boxing teaches you to throw a punch is at a distance such that the punch connects when the arm is fully extended. Unlike retracting a punch, this method maximizes force and minimizes contact time. It's rarely that one performs a perfect punch, but the method is sound.

As for a shockwave effect, I can honestly say I've never felt one myself though in training I've been punched often. So regardless of the physics there, in practice I don't think any human will deliver enough force to cause any such effect to be noticably felt even if it does exist.

 

[DaveC426913]

As for a shockwave effect, I can honestly say I've never felt one myself though in training I've been punched often. So regardless of the physics there, in practice I don't think any human will deliver enough force to cause any such effect to be noticably felt even if it does exist.

Did you really just say 'irregardless'?

 

[TopCat]

Did you really just say 'irregardless'?

Who put the ir- in my word? I swear it wasn't me!

 

[sephirothrr]

Did you really just say 'irregardless'?

What a worthless post.
[The above is a joke. Don't mean to offend anyone]

I looked in the archives, and I found a very similar topic. Here is what is said, roughly a summary of the discussion, with general agreement.

If you throw a punch, without follow through, and it bounces as fast as a jab, then the impulse was very high. If you throw a punch and exert energy to withdraw your fist before reaching the point where your opponents head would have fully stopped the blow then you have WASTED IMPULSE energy because you worked to counter it. If you throw a punch and follow through then your opponent not only feels the full punch but added to that all of the energy you could impart after point of impact...

I like it. I get what I missed now - the W = F/T model assumes a single force applied at an instant. However, a punch is a force that is continually applied.

I have seen the light.

 

[Jeremy_V]

sorry about the worthless post. I just wantted to make sure that what I believe is really fact not fiction.

thanks for all the responses

Jeremy

 

[Jeremy_V]

so back to my question how do I prove my point to these people. if there is some confusion on this board then I am sure its going to be a bit hard to convence these people inless i have a really good explanation.

 

[stewartcs]

You could always punch them and follow through (make sure to really step into it), and then have them punch you and pull their punch like they say too. Keep it up until the first person gives in. I guarantee it won't be you.

 

[DaveC426913]

Set up a mechanical version. Swing a bat at an apple with a post in the way preventing follow-through. Swing the bat at an apple without the post. See which obliterates the apple more.

 

[sephirothrr]

Set up a mechanical version. Swing a bat at an apple with a post in the way preventing follow-through. Swing the bat at an apple without the post. See which obliterates the apple more.

The only problem is, the force of the apple on the post would be an extra reactionary force.
Or is the post blocking just the bat?

 

[DaveC426913]

The only problem is, the force of the apple on the post would be an extra reactionary force.
Or is the post blocking just the bat?

Yes. Blocking. More accurately, stopping the bat 2 inches into the apple. The post is next to the apple.

 

[Jeremy_V]

hey I like that idea with the bat! hey I might even take it a step further and have them hit me with the bat and only go 2 inchs deep I am sure it would hurt quite a bit but then I get a full swing at them with fallowthrough! ha ha I bet if I explain it to them like that the will get the idea even before I hit them. Its so simple to me I can't understand how then can even think it could give them more power. the funny thing is that every time a new person starts the class they have a hard time believeing it but after a few weeks of being brain washed they too are selling the idea to everyone they can. Looking back at it its really funny. my wife said its like a scarry movie where the whole town gets tricked but don't even know it.

again thanks so much for all your help I have a lot better idea of how to present my findings to them now! I have convenced most of my friends of the truth about this already so there are very few people in the class now who believe the lie so things are going good! tonight I am going to class and me and my friend are going to talk to the
teacher about this and present our proof so I will let you guys know how it goes when I get back! wish me luck!

Jeremy

 

[DaveC426913]

hey I like that idea with the bat! hey I might even take it a step further and have them hit me with the bat and only go 2 inchs deep I am sure it would hurt quite a bit but then I get a full swing at them with fallowthrough! ha ha I bet if I explain it to them like that the will get the idea even before I hit them.

I've got to admit, you'd be hard-pressed to be more convincing than that...

"Hi. I'm going to stand right next to the corner of this wall so you can only see two inches of my chest sticking out, and I'm going to let you take a swing at me as hard as you can.

Then I'm going to stand you in the middle of the room and I'll take a swing at you as hard as I can.

What? No one wants to be first? Hey, where's everybody going?"

 

[Jeremy_V]

DaveC426913,
Yea I think that is about the same reaction I would get!
I need to make sure not to make too much fun of them or they will get really mad and not listen. Man is it going to be be easy to make fun of them I am just going to need a lot of self controle.

I can hardly wait to talk to them they are going to half to be compleate idoits to not get it but believe me I have faith that they are still going to try and convence me that I am wrong. "WE BELIEVE IN SCIENCE AND ITS A PROVEN FACT THAT RECOIL CAUSES MORE DAMAGE" yea I am sure I will hear that a lot tonight.

I just hope that i get to use the bat! yea that will be fun I told one of my friends about that idea and he said that I was crazy and that its against the wing chung do code to kill people so he does not think they will let me do the demonstration! ha ha

Jeremy

 

[Jeremy_V]

well I talked to the guys and most of them are convenced that I am right however a few of them are not sure and one of them is still totally convenced that he can make a shockwave that will do 10 times more damage with his 2 inch punch then someone can do with fallowthrough yea I think I might see about having him exammined by a professional to see if he needs to go to the funny farm.

The only thing they could come up with was that the body might not have time to react and tighten up with the 2 inch punch and with fallow through you would have time to tighten up your muscles. I told them that might be true but I still had those first two inchs the same as you and then I had the extra ones as well. they are trying to tell me that you can hit someone so hard that it gives them wiplash from hitting them in the chest. yea sure.

some people never learn.

Jeremy

 

[shukrri]

When you say a follow-through of 2 inches and 5 inches, despite the fact that it looks like a punch, it's actually a push. Clearly pushing someone 5 inches instead of 2 will hurt more...

A real punch, one that'll knock out the other guy, is recoiled, and very fast. Here's why.

1. A change in momentum (in either x or y) is equal to the integral of F(t)dt bound by F=0 on a F vs t graph.

2. As your fist smashes into the target, it changes it's momentum (this change of momentum is called an impulse)

Combining 1 and 2 we get F = $$\Delta$$P/$$\Delta$$t

Since time is a dividing factor, the smaller the contact time, the higher the force of impact. Notice however, that the change in momentum is the force MULTIPLIED by the contact time, therefore despite the much higher force the change in velocity will be very little. This means that most of the energy doesn't go into accelerating the guy's body but rather into stress of the surrounding tissues (causing strain causing them to rip and break apart).

You can prove this at your home or dojo or whatever. Buy 2 big bags of rice and hang them next to each other. On the first bag, throw whipped punches with very fast recoil, notice how the bag won't budge very much. On the other bag throw the followed-through punch and notice the bag will swing wildly back and forth.
After about 10 000 or so punches (you can do this over a period of time, just give it a hundred punches a day each for a couple of months), take down the bags and open them up. You'll see that the grains of rice in the second bag, despite it swinging wildly are pretty much intact, however the grains in the first one are totally destroyed.

There are also tactical considerations advocating the use of a whipped punch, but I'm sure you can figure those out yourself :)

AS a side note, in case you bring this up -

Some people will tell you to aim a couple of inches behind your intended target. I believe this is for mental reasons and not physics. Think of little children first running a 30m sprint in gym class. They'll run and stop at the line. Then the instructor will tell them to stop a couple meters past the line. You'll notice that they then start decelerating only past the finish line and not before, crossing it at maximum speed instead of at a dead stop.
Same principle, only substitute finish line for face and kid for fist :P

Hope this was helpful

 

[DaveC426913]

Since time is a dividing factor, the smaller the contact time, the higher the force of impact. Notice however, that the change in momentum is the force MULTIPLIED by the contact time.

This is a misunderstanding of the application of the formulae to the physical world.

It's the eqivalent of my claiming that, if I'm driving my car and measure its speed at 60miles per hour, I could instead decide to drive to for only 1/2 hour and I would magically find myself doing 120miles per hour simply because I've halved the denominator.



To halve the time yet not halve the energy transfer you'd have to throw the punch correspondingly faster. If you can do that, you've got a correspondingly harder punch. Period. Why bother reducing the time?

 

[stewartcs]

When you say a follow-through of 2 inches and 5 inches, despite the fact that it looks like a punch, it's actually a push. Clearly pushing someone 5 inches instead of 2 will hurt more...

A real punch, one that'll knock out the other guy, is recoiled, and very fast. Here's why.

1. A change in momentum (in either x or y) is equal to the integral of F(t)dt bound by F=0 on a F vs t graph.

2. As your fist smashes into the target, it changes it's momentum (this change of momentum is called an impulse)

Combining 1 and 2 we get F = $$\Delta$$P/$$\Delta$$t

Since time is a dividing factor, the smaller the contact time, the higher the force of impact. Notice however, that the change in momentum is the force MULTIPLIED by the contact time, therefore despite the much higher force the change in velocity will be very little. This means that most of the energy doesn't go into accelerating the guy's body but rather into stress of the surrounding tissues (causing strain causing them to rip and break apart).

You can prove this at your home or dojo or whatever. Buy 2 big bags of rice and hang them next to each other. On the first bag, throw whipped punches with very fast recoil, notice how the bag won't budge very much. On the other bag throw the followed-through punch and notice the bag will swing wildly back and forth.
After about 10 000 or so punches (you can do this over a period of time, just give it a hundred punches a day each for a couple of months), take down the bags and open them up. You'll see that the grains of rice in the second bag, despite it swinging wildly are pretty much intact, however the grains in the first one are totally destroyed.

There are also tactical considerations advocating the use of a whipped punch, but I'm sure you can figure those out yourself :)

AS a side note, in case you bring this up -

Some people will tell you to aim a couple of inches behind your intended target. I believe this is for mental reasons and not physics. Think of little children first running a 30m sprint in gym class. They'll run and stop at the line. Then the instructor will tell them to stop a couple meters past the line. You'll notice that they then start decelerating only past the finish line and not before, crossing it at maximum speed instead of at a dead stop.
Same principle, only substitute finish line for face and kid for fist :P

Hope this was helpful

I refer to my previous comments found in post #7.

CS

 

[shukrri]

I believe they are confusing the effective force "felt" by an object due to the objects momentum divided by contact time. Remember the old analogy of catching an egg without breaking it? If you allow enough time (by moving your hand away from the egg as it comes into contact with you) to absorb the momentum, the force you "feel" is less. Hence the egg doesn't crack.

It seems we agree... if you pull back fast, you're not giving your target any time to absorb the momentum, therefore "cracking the egg".

The problem with what they're telling you is if you are pulling the punch back, you are negating the force you are applying. So how could the other person feel more force by you reducing the force you're applying??

You aren't negating the force you're applying by pulling it back. As it travels through the air it gains a lot of momentum, but once it comes in contact, due to the added resistance of your target, the gain in momentum is almost negligeable.

As for the car analogy, it's just wrong. If you travel 30 or 60 minutes, it doesn't matter as traveling with a constant speed produces no change in momentum and thus no force. Think of it more as a car that goes from 10m/s to -10m/s in 2 seconds versus a car that does the same in 1 second. The 1-second car will have twice the acceleration and thus twice the force of the 2 second car.

 

[kateman]

shukrri is completely right

martial artists have been teaching this idea of retracting the punch throughout the centuries. i have learned never to question them or what they teach.

that and also my physics teachers have also told me exactly the same thing about this same topic.

 

[DaveC426913]

Think of it more as a car that goes from 10m/s to -10m/s in 2 seconds versus a car that does the same in 1 second. The 1-second car will have twice the acceleration and thus twice the force of the 2 second car.

Exactly, a car that can accelerate twice as fast can do so because it is a faster car; it is analagous to a punch that is delivered faster. If you can deliver that punch twice as fast, it will do more damage and has nothing to do with whether you recoil or not.

 

[stewartcs]

You aren't negating the force you're applying by pulling it back. As it travels through the air it gains a lot of momentum, but once it comes in contact, due to the added resistance of your target, the gain in momentum is almost negligeable.

Your fist is gaining momentum because your muscles are producing the force. If your muscles then reverse the direction of force at the moment of contact, then the force you are applying is reduced.

Look at professional boxers; they always step into their punches. If they connect, their opponent is normally knocked out. However, with jabs, very seldom is their opponent ever knocked out.

What you seem to be failing to realize, is that the impulse is a function of both the applied force and the change in time. If you reduce the change in time (contact time) by reversing the force (it is reduced due to you pulling the punch backwards) then the impulse is also reduced because the force is no longer constant (it is now reduced). Hence the impulse is less at well.

CS

 

[stewartcs]

martial artists have been teaching this idea of retracting the punch throughout the centuries. i have learned never to question them or what they teach.

That's how ignorance is spread, not questioning rediculous theories.

that and also my physics teachers have also told me exactly the same thing about this same topic.

I really doubt your physics' teachers have said this. If so, you should change schools.

CS

 

[seycyrus]

This tomfoolery is often discussed in martial arts newsgroups. WC practictioners conveniently forget to recall the origin of the quicker change in momentum.

They also fail to provide actual footage of a WC practitioner using his WC strikes to devastating effect. It is ALL anecdotal

If I were to shoot a cannonbal that was somehow tethered so that it would feel a "pull back" at 2 inches after impact would it do more or less damage than a cannonball thta was allowed to travel ALL the way through it's target?

 

[seycyrus]

shukrri is completely right
martial artists have been teaching this idea of retracting the punch throughout the centuries. i have learned never to question them or what they teach.
QUOTE]

Ahh, grasshopper. You SHOULD question both them AND what they teach. It will allow you to become exposed to greater truths.

Thinking about "retracting" the punch often allows for a faster punch. It's psychology.
It also allows ensures that your hand is back in position for another tehnique.