power explained.where are the engeeners who take up hobbies?

[mai tai]

i know pockets hate people who use physics to explain things. but i dont believe in the ki. or any other chop suey stuff.

in my opinin we live in a physical world and we cant escape that.

when we say power we are not refering to the scientific term but more as to how much damage on inflicts with there fist.

if you want to use a formula us the kenetic energy formula.

2

KE=1/2 mv

or one half times mass times velovity squared.

by watching this you can see how how hard you can hit takes into account speed size and technique.

first speed...... by the formula this is by far the most important.

if you could increase your speed you would hit much harder.

however while this is possible (form, explosive weigth training and plyometiric).

it is also very diffecult to make great gains. for example last yeat at the corporate challenge i ran the 100meter i ran an 11.2

if i could improve my speed a scant 10% i would be a world class sprinter.(instend of a science geek posting on the internet).

next is mass obviously if you can improve your mass you would hit harder also.(providing you dont sacrifice speed).this is why big guys hit harder.

if your trying to get bigger so you can hit harder becareful.if you compete in a weight class sport. (boxing ,nhb, muay tai, wrestling jujitssu)

because an artifically big person will not have the larger bone structure to take blows or the reach advantage of a naturally big guy.

this last part is technique...by throwing a propper strike you will move faster and your mass will be higher. ie if you just arm punch it will be just your arms mass. if you turn your shoulder and hip into it it will be a much greater increase in mass

[JusticeZero]

There's also the dynamics of how the force rebounds from the elasticity of the target, and most people seem to increase the force and dynamics of their blows in that and increasing mass by striking with more concentrated use of the torso rather than a hand in isolation.

[Mr Pockets]

Hahaha! I only hate when people try and talk physics in here because they usually get it all wrong, just using their basic physics 101 knowledge.

It's funny you mention that too- because I am an engineer. (I also cringe when people start talking ki and stuff.)

To respond quickly, first to mai tai- it's not so much about kinetic energy as momentum. The derivative of momentum is force, and force is what hurts you when you get hit. (This is why when impacts take longer, like falling on a pillow instead of concrete, the total momentum transfer is the same but it hurts less- as the maximum force at any time is less.) Now we all know the general equation for momentum is MV, mass times velocity. But in terms of punches and kicks, you can't really measure the "mass" behind a punch, the best you could do is measure the velocity of a mass that you punched and see what happened, if you can account for the natural energy losses.

As for what justice wrote- the rebound you refer to is different than how you're thinking. The elasticity of an object matters only in how long the impact takes when it hits you. If it's a harder object (metal, rock, bone...) the impact takes a fraction of a second and the maximum force experienced is huge as compare to... if the object is soft (pillow, spring, etc) the impact takes a long time and the maximum force you ever experience is much smaller. An interesting factoid- if you drop a bouncing ball and it bounces to 90% the height of what it was dropped from, the total momentum experienced by the floor it boucned off of was 190% of the momentum it had falling, right before it impacted. This is why being thrown to the ground hurts so much, and why knuckles hurt more than gloves, and brass knuckles hurt more than that. (Harder objects "bounce" more momentum back into whatever is impacting with them.)

The reason that using their torsos with their punches (that is, punching from their hips) is because that generates more force than you could hope to from your arms alone. (As it turns out, from baseball to boxing to jiujitsu, all your "power" comes from your hips.) This is why over half (I think the number was 60%?) of you punching strength comes from your legs, next your torso, and finally (something around 10-15%?) comes from your arms and chest.

[Mr Pockets]

Whoa... did I lose everyone?

[Mr. Mike]

yes and no. I understand what you are saying, but unfortunately it is rather dry at 3:30am. So, my silence was to mean that I do not have a retort, since you sommed it all up.

In fact, I may just print that and hand it to the next jerk that insists 'speed equals power.'

[ninjanurse]

No. Sensei always put more emphasis on leg strength, balance, and hip movement for a reason!

[white lily]

good summation...

just a quick addition... the NSCA journal of S+C Reasearch published at study of punching in boxing in '91 (I think)

the reaserchers concluded that 39% of punching power came from legs, 37% from torso and 24% from arms.

You could argrue that boxing punches and MA punches are different I guess... but it does give a foundation to work from.

[yamesu]

AAAAAAARRRRRRRRRRGGGGGGGHHHHHHHH!!!!!!!!!!

I just typed out a ripper post, and my browser crashed.

Basically:

Cheers for the thought provoking read. Its good to hear from some scientific members of the MA community.

But the universal concepts of kinetics cant really be explained using

KE=1/2mv^2

(though it works well with falling bricks.)

For example, we cant use the above equation to find the kinetic energy asocciated with the sigma-bond between two carbon atoms. (Can you tell im a chemist?)

More equations are introduced into the world of physics as new findings are continually unearthed.

This post really deals more with the realms of Kinesiology and Physiology, as opposed to Classical physics.

Cheers again.

[yamesu]

The derivative of momentum is force,.

Ummmm......wont the derivative of momentum be acceleration......

f'(x) = [f(x+h)-f(x)] / h

and force is what hurts you when you get hit. (This is why when impacts take longer, like falling on a pillow instead of concrete, the total momentum transfer is the same but it hurts less- as the maximum force at any time is less.) Now we all know the general equation for momentum is MV, mass times velocity. But in terms of punches and kicks, you can't really measure the "mass" behind a punch, the best you could do is measure the velocity of a mass that you punched and see what happened, if you can account for the natural energy losses.

Pressure is what hurts you when you get hit.

Pressure is a given force over a given area.

Thus,

Concentrate the same amount of force into a smaller area, and you have greater pressure.

The pillow thing works as the structure, aeration/porosity and density of the pillow are thus that; the force exerted on the pillow will be spread through it much more readily than a concrete-block. (Think S- and P- waves.)

This changes the way the force travels through the object, NOT the actual amount of force exerted on the object due to applied pressure.

Wow, this post really got me thinking back to my first year uni days.

Cheers again for the interesting read.

[ovine king]

The biggest reason why physics shouldn't be used to describe how power/force/energy works in martial arts is because we are not point masses in a vacuum.