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/sci/ - Science & Math

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3949919 No.3949919 [Reply] [Original]

Ok /sci/. I do a lot of martial arts and one of the martial arts I want to get in is Judo simply for the throws and holds. One of the things I've always heard is the saying "The bigger they are. The harder they fall. How true is that? It seems to be somewhat logical to me. A 60 kg man getting slammed at the same speed a 100 kg man is slammed at probably wouldn't be as devastating. However there is the fact that you can slam a 60 kg man a lot faster then 100 kg man and kinetic energy is a lot stronger with increased velocity than mass.
Help me /sci/!

>> No.3949955

Bump. Will a smaller man getting slammed at the same speed as a big man get hurt more or less? What if it was faster? Would it be negligible?

>> No.3949959

If an object expands by the same ratio in each dimension, and maintains its original density, then there will be a higher weight/surface area ratio. Thus on impact, each unit of surface area will experience a greater collision

>> No.3949983

f = ma

>> No.3950006

>>3949983
What about k=1/2mv^2

>> No.3950038

Let's say hypothetically speaking I slam a 100 kg man. Let's say I slam another man that is 50 kg twice as fast. Who takes more damage?

>> No.3950069

Momentum is a conserved quantity. Energy would make sense for a punch, because of the point of punching someone, but takedowns are about momentum.

>> No.3950095

>>3950069
What about the point of the slam....

>> No.3950127

If you're throwing to the guy to the ground, you have to consider that gravity is going to help you out. If you were fighting horizontally (think sumo wrestling), extra weight makes you harder to move. If you throw a heavy guy off balance, he needs to work harder to stay on his feet than a guy who's lighter. Likewise if you let go after the throw, he'll hit the ground with more force than a lighter guy because of the extra mass.

>> No.3950128

>>3949983
this.

And don't forget inertia. It's what the "m" in that equation is about.

>> No.3950146

>>3949955
depends on from how high they are thrown and how they fall.

>> No.3950165

>>3950146
That's what I am asking.

>> No.3950211

>>3950165

if youre trying to determine at what final speed would a 60kg man have to be hit the ground (starting at rest?) such that impact is just as "hard" as the 100kg man, set the 60kg's final kinetic energy equal to the potential energy (initial of course) of the 100kg man and solve for v. from this you can also obtain the height at which the 60kg man had been "dropped" as well, that is, if you know the initial height of the 100kg man.

I really dont know if this helps though, it's hard to tell what you are asking exactly.

>> No.3950233

>>3950211
In simplest terms, I'm asking if the extra speed in slamming a little guy would cause more damage because V increases K geometrically compared to M increase arithmetically. Or does it sort of even out? I don't have any hard numbers so its really all speculation.

>> No.3950281 [DELETED] 

>>3949955
depends on from how high they are thrown and how they fall.

>> No.3950326

Judoka here.

The best Judo players tend to be short and stout. They have a lower center of gravity, which makes them more difficult to throw. Tall guys are easy to tip over. Weight doesn't really help much either, since the throws are all about leverage. I've seen little 100lb women throwing guys twice their size with ease.

So to answer your original question: yes, more weight=harder fall. Although breakfalls are a large part of Judo, so it doesn't really matter anyway.

>> No.3950341

>>3950233
All collisions are determined by momentum because momentum is a conserved quantity.

>> No.3950424

>>3949919
>However there is the fact that you can slam a 60 kg man a lot faster then 100 kg man a...

Not so, you rely on gravity to do the slamming, not your own muscles. As a BJJ player I can confirm from experience that heavier = harder falls, as a mathematician its just plain obvious.

>> No.3950458

ITT: a bunch of people explain simple elementary physics to OP but he is too busy gargling dicks to understand.

Force = mass X acceleration
More force = more pain

If mass is cut in half and speed(acceleration) is doubled force stays the same.
Im no judo expert but im assuming its more of a forcefull drop than it is a throw so we will use gravity as our acceleration

Force = mass X 9.8m/s^2
Now the only variable that can effect force is mass. More mass = more force.

Ta da! The bigger they are the harder they fall.

>> No.3950465
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3950465

>>3950458

>speed(acceleration)

>> No.3950490

>>3950424
>as a mathematician

work more on your physics. When the man is dropped, he is in freefall. At that point additional acceleration of the man toward the ground, if more than simply mg, is due to whatever external force is applied, which would be your pushing down on him. In such a case, both gravity and your arm are doing work. In other word, energy is being transferred in two different ways, by the force applied by your push and gravity (neglecting air resistance).

>> No.3950501

>>3950038
the 50kg guy takes twice as much damage in this case.

>> No.3950811

>>3950490
You're missing the point. Consider the total force applied (that of any 'pushing' you might do + that of gravity). The force applied by gravity depends on their mass, the force applied by you does not. The acceleration from gravity doesn't depend on the force, the acceleration by you does. So what we have it acceleration caused by gravity + acceleration proportional to the amount of force you apply downwards (realistically this is negligible, since you don't push people towards the ground very much at all, but for the sake of argument let's consider it anyway). Let's look at the example of a person having mass 100 standard units, and you applying 100 standard units of force, resulting in 1 standard unit of acceleration (a = F/m), so they accelerate at g+1 for let's say 10 time units, to reach a velocity of 10(g+1), for a person half the weight they reach the velocity 10(g+2), now momentum should be given by p = mv.

Now we have for the lighter person
50*10(g+2) = 500(g+2) = 500g + 1000 momentum units
For the heavier person
100*10(g+1) = 1000g + 1000 momentum units

Its fairly clear now that the heavier person is required to dissipate more energy than the lighter person - hence the 'harder they fall' saying.

>> No.3950820

Chuck a bony person on their ass, ass cracks.
Chuck a fat person on their ass, comfortable safety pillow.

>> No.3950833

>>3950458
haha forceful drop ... you sir have never been judo thrown

http://www.youtube.com/watch?v=rRNHFuNL0mc

>> No.3950836

So you guys never learned Newtonian physics?

<span class="math">F = \dot{p}[/spoiler]

Second law of motion. It means, the force is greater if the _change_ in momentum is greater. Since momentum is <span class="math">p = mv[/spoiler], we get:

<span class="math">F = \dot{m}v + m\dot{v}[/spoiler]

>> No.3950847

You also have to take into account durability and pain threshold.

I'm 6'3", got in a friendly scrap with a judoka friend of mine.

He did manage to pull three over-shoulder throws on me, dropping me on to hard, frozen dirt. He's a bit of an asshole like that.

I got up each time, because I don't feel pain, even of serious injury, for HOURS until the fight is over. I'm too excited at the time.

So, although the falls were pretty hard, I was able to keep fighting.

>> No.3950849

>>3950847
>2011
>not kicking people when they are down

Well, just because it was a friendly fight I hope.

>> No.3950852

>>3950849
>>2011
>>Implying I can't fight and defend myself to the full degree I can when I am standing

>> No.3950857

>>3950852
Wait....Okay.....maybe I can't hit him in the face effectively until he's on the ground too.

>> No.3950859

>>3950849

> >not kicking people when they are down

Wow, you're a pussy.

>> No.3950863

>>3950859
And I'm damn proud of it.

>> No.3951064

>>3950852
So what's your ground game? Because it sounds to me from your story with the judoka that you're not exactly brilliant at BJJ or sambo or greco or any such thing. If you have no ground game and you honestly believe that you're just as good on the ground as standing you've got another thing coming.

>> No.3951105

>>3950811

OP, listen to this guy.

>> No.3951443

>>3950465
I was simplifying for OPs tiny brain. I am unsure if he understood what acceleration is

>> No.3951578

uniform gravity doesn't depend on the mass of the object in question since for all objects <span class="math">F_{gravity}=m g[/spoiler] roughly speaking, so then <span class="math"> m a=m g \rightarrow a = g[/spoiler] so the force on the 100kg man is <span class="math">\frac{100}{60}[/spoiler] times that of the 60kg man