Re: Force from punch


It's an excellent question.
That was refreshing :-)

I assume that when you plant your feet and exert a push to the wall of
42 kg, then you are using more than the body mass you can lever
against the wall. You are also using muscle strength.

I actually push the floor away from the wall at an angle. From a
standard zenkutsu dachi (deep forward stance) I will lift up my
leading foot from the floor, if I push any harder.. yet, if stand very
very deep and my rear foot does not slide, because it is pushing up
against a corner between wall and floor, I can push 115kg with one
arm.

I would also
guess then that not all of this "42 kg" force is available when you
throw a punch, though some of it is. When you throw a punch, some of
that force translates into accelerating your fist and arm to 9.5 m/s.
I suspect that taking the full 42 kg as being available as a moving
mass is double-counting somehow.

I suspect not. At the end position I push with 42kg (the awkward way)
and at that time my fist is moving over 9m/s. At the point of contact
I therefore already have the velocity, or do I misunderstand you?

So bottom line: the force of your punch will depend on how big the
thing you hit is, and how soft.

I realize that much. That is why you do not put on a big soft glove
when you hit concrete to break it with your hand... and why you do it
to avoid breaking an oponents facial bones.

One extreme is two infinitely rigid objects colliding which will
generate an infinite acceleration due to an infinite force. That is
not possible in the real world, but let us assume for a moment that we
have a fist hitting a wall and that the fist deforms so that the
collision force works over 5mm.

That will mean that the deceleration is 9m/s /5mm which takes 1,1ms.
The acceleration is then 8100m/s^2 and the force is 8100*mass Newton,
but... what is the mass? If I rip of the arm and throw it at the wall,
lige a spear, the mass is (wild guess) 5kg, but that is not the case.

If the arm was a spring which is fixed in one end and has a fist in
the other and it had been compressed and let free so it has pushed the
fist forward with 9m/s and the spring force at the compression, which
exist at point of contact, is 430N, then what does this compare to for
the example slow down length of 5mm?




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Relevant Pages

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