Punch and Kick Force?

[JackJack]

F=m*a is indeed force, but the 'a' and 'm' you have to consider is the acceleration and mass of the object that's been hit. Whatever the truck has been doing in the seconds, hours, or years prior to the impact is irrelevant.

true...very true. What the truck was doing is irrelevant and that is why the formula for force is irrelevant as if you look up the formula for acceleration, time is a variable. If you say time is not a factor, then you can't use the formula.

No, it can't. Joules is energy. Pressure is excertion of force. They are completely different things.

Try looking up formulas to convert Joules to ____. You will see that 1 Joule = 8.89.... PSI.

And you are also wrong in your conclusion. Let's consider a strike to the head, bareknuckle (small area) or with large boxing gloves. The smaller the target, the more localized damage. But the impact on the brain will be identical to the hit that was done with the gloves. Impact energy is transferred to the brain via the skull. How that energy got delivered to the skull (wide or small area) is irrelevant.

The kinetic energy is the same and eventually, the same amount of energy is delivered to the brain, but the brain was not the impact area. The impact area may have been the whole side of the head or just the temple, all depending on the type of strike.


I am giving you straight simple physics. If you don't believe the physics, go look up the formulas yourself and study up on what they mean.

 

[Bruno@MT]

Try looking up formulas to convert Joules to ____. You will see that 1 Joule = 8.89.... PSI.

No it is not.
Joules is energy.
PSI is pressure.

They are 2 different things and cannot be converted to one another without putting them in a context where that makes sense, and which highly depends on parameters.

See here for possible direct conversions.
http://www.fact-index.com/j/jo/joule.html
1 joule can be converted to many other measures of energy. There is not a single conversion to pressure.

The only way to convert joules to psi is by doing an impact calculation, taking into account mass, density, structure and other parameters to calculate how much pressure is created for how long, to cause which deformation.

Blindly saying that x joules is y PSI is just rubbish.

I am giving you straight simple physics. If you don't believe the physics, go look up the formulas yourself and study up on what they mean.

I have a masters degree in engineering.
I know exactly what I am saying here. I very much doubt that you do. If you do, then please show me those straight simple physics that you are talking about.

 

[Bruno@MT]

But in case that is too complex, I'll explain it with a simple example.
You know about air friction, right? If we discount gravity for a moment, suppose you shoot a bullet in the air. The energy of that bullet is n joules.

Air friction exerts a pressure on the bullet, making it slow down.
This air friction is very, very low, or the bullet would stop quickly. Instead, the bullet takes a long time to decelerate because not much pressure is generated. Now shoot the buller in water. Higher friction coefficient means the bullet stops rapidly. Much pressure is generated.

So you see a direct conversion from joules to pressure is impossible.
And if we now add in surface area, shape of the objects, structure, elasticity and plasticity of the target AND the bullet, it becomes a very complex calculation to see how much pressure is generated at any given moment.

 

[seasoned]

Welcome to MT JackJack and Actionmanrandall! Why don't you pop over to the Meet and Greet section and say hello, I promise you'll get a warm welcome and we'd love to hear about your styles/arts.

Ditto that, and as Tez3 has said, stop over.

 

[geezer]

...So you see a direct conversion from joules to pressure is impossible. And if we now add in surface area, shape of the objects, structure, elasticity and plasticity of the target AND the bullet, it becomes a very complex calculation to see how much pressure is generated at any given moment.

So complex to calculate, yet so easy to feel... especially if you are on the receiving end! That's where a good trainer holding focus mitts, a kicking shield, Thai pads and the like can be so much more helpful than a calculator!

 

[JackJack]

I have a masters degree in engineering.

Then you need to stop being so argumentative. If you truly have a masters degree, you would know that the formulas are meant for a perfect environment....aka, no gravity, no friction, no air, and 100% efficiency conversion of energy to work. So your argument of friction is needless.

http://www.unitconversion.org/unit_converter/energy.html

Does this environment exist, no, it doesn't, but that is the physics. However, I think you are getting way too wrapped up into technicalities to see the real point. The real point is, you can't measure the effects of an impact using the force formula.

http://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

http://wiki.answers.com/Q/What_is_the_formula_for_force
Force = Mass * Acceleration

Force is the pull or push of an object, not the effect of objects colliding. Pressure is created when objects collide. That pressure is created by energy....kinetic energy created by mass and speed (1/2 m * V squared).

Now lets take that truck again. I am in a truck sitting at a stop light. The light turns green and I slam on the gas. I am accelerating very fast, but in just 20 feet I run into a wall say at 20 mph. The truck will have a pretty dented in bumper but that's about it. Now lets say I get out of the truck and get into another truck of same model and I start driving on the highway and then decide I want to run into a wall again going at 50 mph. I know, I'm pretty stupid huh...but on with the point. I'm not accelerating much if any at all, but I do hit the wall at 50 mph. That truck is going to be demolished and I am going to be dead and the wall is going to be damaged.

Now, because we live on earth where there is gravity, the truck had to be constantly provided power to keep the speed at 50 mph, but according to the formula for acceleration, the acceleration was zero so the force "would" have been zero if there wasn't gravity and friction, but because there are those variables, a force (the engine) had to be applied to keep it going. As for the impact effect, well, the kinetic energy applied in the second accident was way more than the first.

Lets take the KE formula and given the truck weights 5,000 pounds.

ke = 1/2 kg * m/s squared

5 000 lb, lbs = 2,267.96185 kilogram

so accident #1:

20 mile/hour (mph) = 8.9408 meter/second

90648.05904622899 = 1/2 (2267.96185) * (8.9408) squared

90648.05904622899 = 802,302.92712012 psi


#2
50 mile/hour (mph) = 22.352 meter/second

566550.3690389312 = 1/2 (2267.96185) * (22.352) squared

566,550.3690389312 joules= 3,698,426.6957275 psi


As you can see, there is a big difference. The truck with no acceleration but traveling at 50 mph creates 6.25 time more kinetic energy then the truck that is accelerating very fast but only traveling 20 mph. Now you can agrue all kind of techicalities on the conversion from joules to psi all you want, but take it up with the makers of the site who I get the conversion from (http://www.unitconversion.org/unit_converter/energy.html), but I think you can clearly understand with this example the flaws in using the force formula to determine the effects of two objects colliding.

 

[JackJack]

Now my question to everybody here is, is DeLamar (see page one) and I the only ones who understand this, or are you just being quiet?

 

[JackJack]

Sorry...I left something out.

I gave the environmental factors, gravity and friction, in dealing with the force formula, but not for the kinetic formula. Well, there isn't much the environment can effect during impact, of the amount of energy created, however, there are variables that effect the direction of the energy/psi. This is where base, material and all those other things my commenter was so kind in pointing out. Lets look at the accident #2. The wall was solid and very strong, so it had much less damage then the truck, so most of the energy was redirected back into the truck as it could adsorb it better. The same KE/pressure was created, but where it went was effected by those parameters.

This is very important in martial arts and why some styles preach a solid base. It is also why Bruce Lee preached muscle tension throughout the body right at impact. You are not supposed to have muscle tension in delivery of the strike because that slows down the strike, but having muscle tension during impact is a resistance against your body absorbing the pressure from the impact. So, if you have a solid base and solid body during impact, the pressure should be delivered towards your opponent.

I think we can all at least agree on this.

 

[Bruno@MT]

Then you need to stop being so argumentative. If you truly have a masters degree, you would know that the formulas are meant for a perfect environment....aka, no gravity, no friction, no air, and 100% efficiency conversion of energy to work. So your argument of friction is needless..

I used that argument to point out that you cannot directly convert energy to pressure.
Pressure can be the result of an energy impact, via various calculations. But they are 2 different things, whereas in your previous posts you said that you can directly convert one to another.

this is not about me being argumentative but about you saying things which are incorrect, and to which I respond. For example, here you say this:

What they don't understand is force (f = m * a) is the formula to measure the energy it took to get the object moving at that acceleration and speed

Where you imply that force IS energy, which is definitely not correct. Force multiplied by the distance over which it is exerted is energy (E = F * d). Force itself IS NOT energy. If you don't want people to be argumentative over such things, then just don't say them, and don't build an argument around them or try to gain credibility by sounding scientific.

 

[mook jong man]

 

[Bruno@MT]

Yeah back when I was in college and a theoretical physics nerd, the ladies were just swarming all over me....
Ok ok. They were swarming away from me... but DEFINITELY swarming I say...
:rofl:

 

[JackJack]

You are correct Bruno, energy is not pressure and I made a BIG mistake in what I was saying earlier. Kinetic energy is not created during impact. Energy is never created, only transferred. A moving object, at any point in time, will have X amount of kinetic energy. That energy is transferred to pressure during impact.

However, that mistake is not as big as using the wrong formula (force) to determine the amount of pressure like that video was making. I felt insulted by watching that video. I, who have about an hour's worth of studying physics seemed to know more about it then they did but yet they were calling there video science. How can they call it science when they have absolutely no idea of the basics of physics?

Another point I should have made about that video is that they were giving the results of the kicks in pounds. Even the force formula calculation gives off Joules, not pounds, so they didn't even understand the formula for force, let alone knowing it was the wrong formula.

 

[Bruno@MT]

No problem.