Physics of Kendo

[dajurama]

Maybe the Newton's Second Law of Motion, F=ma, can explain the hitting power in `N.' If th Shinai weight is 0.5kg, the distance shinai's tip travels is 2.5m, and the performing time is 0.5sec, the power you hit in your opponant's head is 5N. As you reduce the reacting time, the power will be greater~

[Dezza]

42...

[hl1978]

Its a bit more complex. What about additional power due to the kendo players mass? How much of that due to a forwards component? How much due to a downwards component?

[Halcyon]

As a former physics PhD candidate, I can tell you that F=ma is very limited in its application to the real world because the systems you're looking at in the real world are usually so complex. Every calculation began with something like the following: "Let us assume the kendoka is a sphere."

[ender84567]

first we assume a spherical cow......

[Neil Gendzwill]

Even in the most simplified model I can think of (a lever with the right hand as fulcrum) there's more force involved than just the moving mass of the shinai.

Physics is hard!

[tagonagy]

Can anyone explain the advantage of using the left hand with physics?

[hl1978]

Can anyone explain the advantage of using the left hand with physics?

You can create a longer radius arm with the left hand than the right. Try locking your right elbow and keep a loose grip with your left, then try locking your left elbow, and a loose grip with your right.

This leads to greater torque (r x f) with r=radius cross Force and greater tip speed.

Note the above is not the only reason.

[verissimus]

I suspect the physics of kendo have less to do with force (from slamming the shinai down) and more to do with impulse (from tenouchi).

[T.Dehn]

Pardon me sir, would you mind holding off your attack and standing still whilst I calculate the necessary angle, force, and momentum needed to properly score upon your Men?

Whoa! Hey! You moved!
darn it..

[FastKendo]

with the proper tenouchi, I guess the mass is the kendoka+the shinai. In every MA I know, each hit should consist of all of our body mass. But then we need to calculate the speed of the kendoka and the speed of the shinai, don't forget to include the gravity coefficient and then... OMG I'm getting dizzy.. :D

[turboyoshi]

The actual force equation would be a little more complex than that. For one, you forgot to include the force of gravity. Also, the mass of the shinai isn't the only mass involved. It might just have been a poor word choice but reaction time also has nothing to do with it. However, when speaking about mathematics or physics, precision in language becomes critically important. What exactly are you getting at anyway?

blah I took too long to type this but I think I figured out the answer to the last part. Is this what you call post padding? :wink:

[rfoxmich]

Power isn't force. The original question does not make sense. However one thing to consider is that some of the competitors these days are fast enough that when you do the calculations you may have to so some relativistic corrections. Specifically the shinai mass and length will be different in the frame of reference of the sakigawa and time, of course will move more slowly in that frame than in the rest frame of the attacker.

In any event, the collision is inelastic which severely complicates the calculations you'll want to do (the shinai deforms and the men deforms).

Other than that, it's a piece of cake and I leave it as an exercise to the reader.

[Mick]

All I know is Mass of kendoka + mass of shinai + speed of shinai + impact on Kote = OUCH!!!

[JByrd]

However one thing to consider is that some of the competitors these days are fast enough that when you do the calculations you may have to so some relativistic corrections.

:)

It does seem that the more precise you want to be, the more difficult it is to account for all the factors. General principles can still be applied, though.

If you want more kinetic energy from an object (for example, the sword tip), you'll get a bigger payoff by increasing its velocity than by increasing the mass. A bigger swing moves the tip over a larger distance in the same amount of time, which means higher velocity.

If you want to maximize total energy output, you want the energy of each contributing component to combine constructively with the rest. If the energy coming from your legs is out of phase with the energy of your swing, they won't add up. The technical term for the proper phase coordination of energy sources is "ki ken tai no itchi."

If you want to initiate movement quickly, you can't have slack in the components that must be taken up before power can be transferred. A little tension behind the left knee is an example of taking the slack out of our stance.

[Martino]

um why don't you just strap some weight scales to someones head and measure the may value......

[Fudo-Shin]

I bet takanabe senshu secretly cracked this formula... that's why he has the fastest men in the east!!;)

[dajurama]

Takanabe didn't actually hit the `men.' You can see it from its slow motion version on youtube.com. However, Uchimura did admit his lost by `men.' A article said, if you came from outside of Japan, it would be real hard to understand it. So maybe rather timing than speed...I'm not sure yet...

[Bokushingu]

Speed is a component that improves timing. Without a fast smooth technique, you can't out time an opponent. Without an understanding of timing, you can't defeat any opponent. Of course speed relies on form & efficiency, and timing relies on awareness.

[cr720]

...Of course speed relies on form & efficiency, and timing relies on awareness.

When I first read that, I thought you had posted "and timing relies on awesomeness."

Made me laugh, I had to share real quick :D

[Bokushingu]

When I first read that, I thought you had posted "and timing relies on awesomeness."

Made me laugh, I had to share real quick :D

well you could say awesomeness relies on timing... ^_^

[ender84567]

there is no charge for awesomeness, or handsomeness...

[Bokushingu]

there is no charge for awesomeness, or handsomeness...

LOL. Are you sure there's no charge? because i would like to replace some of the "crappiness'" with some "awesomeness'" in my kendo ^_^