# B Which is easier to knock down: A tall or a short person?

1. Mar 30, 2017

### Trance-

From practice (pls don't call police), I know that it is much easier to knock down short people. A tall person of equal mass is more difficult to knock down on the floor. Theoretically, the taller person should be easier because there's this whole center of gravity thing. But in practice, one can feel another factor playing in: Elasticity. Taller people tend to be more 'elastic', so to say, so it's foolish to expect them to be on the floor even after your mightiest punch. Even if they go off balance, they quickly recover. Shorter people? umm not so much.

But I have a feeling there's something more. I cannot reconcile how the defense of elasticity and the weakness of center of gravity combines to make it more difficult for me to knock down tall people. The inverse applies to short people. So what is the physics behind it? Assuming that force is applied on the chest area, what happens between the moment I shove and the moment they fall?

2. Mar 30, 2017

### Staff: Mentor

They resist?

3. Mar 30, 2017

### Staff: Mentor

Tall people are definitely easier to knock down than short people of the same mass. If you believe the reverse then you are doing it wrong (or you may be comparing people of different mass).

For a proper throw you want to get below your opponent's center of gravity, move their center the direction you want them to fall, and prevent them from recovering their balance.

If you want them to fall then you should use a sweep or a throw, not a punch.

Last edited: Mar 30, 2017
4. Mar 30, 2017

### A.T.

Yes, it's also easier to balance a long stick, than a short one.

5. Mar 30, 2017

### zwierz

it does not depend on man's height it depends on the vestibular apparatus endurance

6. Mar 30, 2017

### Trance-

But shouldn't 'flexibility/elasticity' have some role in here? At least it has always felt to me that way. The idea that tall things should be easier to fell assumes stiffness (e.g in case of trees). But with people, you have flexibility to account for too. I had one guy who was 6'1, 75 kg, and another who was 5'9, 75 kg, and I always had an easier time shoulder pushing the latter; he'd fall at one sudden push. The former, however, was more difficult to deal with. I'd push him and he'd only swing to one side and then back to original position.

7. Mar 30, 2017

### Drakkith

Staff Emeritus
Don't forget that humans tend to adjust themselves so that they don't fall over if they can help it. For one, tall people typically have longer limbs and can present a wider "base" when they spread their feet apart. Also, don't overestimate personal experience. The shorter guy that was easier to push over may just not be very good at keeping their balance, whereas another might.

There are undoubtedly many varied factors that we can't begin to predict here.

8. Mar 30, 2017

### A.T.

But tall things are also easier to balance, because they fall over slower. A tall person has more time to react.

9. Mar 30, 2017

### Staff: Mentor

Sounds from your description that it was more related to their skill/strategy than their size. The latter tried to resist and the former used deflection.

In general, this is why a good scientific study is difficult to conduct. You need more than one pair of data and you need to identify and address confounding variables.

10. Mar 31, 2017

### CWatters

Isn't it the case that tall people have longer legs so they can get them further apart improving stability?

11. Mar 31, 2017

### Staff: Mentor

My experience is that weight matters most, then skill, then height. But where height matters it seems to be a disadvantage.

However, my experience is anecdotal and basically consists of a single martial art at a single school.

12. Mar 31, 2017

### Khashishi

Tall people have larger moments of inertia. So, it's harder to rotate them. But it's easier to get under their center of balance. It depends on the details of how you knock them down.

13. Apr 2, 2017

### Trance-

Thank you all. I got my answer for my contrary-to-theory experience. These are the factors I gather: a wider base, a bigger reaction time, and a larger moment of inertia, play in favor of tall people (given all other factors like skill, where the force is applied (i.e the upper half), and weight remain constant -- which is difficult to attain but 'approximations!').

.

14. Apr 3, 2017

### woody stanford

Being a former street fighter and practitioner of physics, I think I can shed some light on the subject.

You might be right about it making physics sense that knocking a tall person down might be mathematically easier. However I would point out that physics is merely a subdiscipline of Truth and your question begs the entry of a multidisciplanry approach here (I'm going to talk a little about psychology an such).

You have ignored the relationship between the pusher and the fallee. You are concentrating on the object, but the subject has just as much to do with (if not more) the situation as the object. In that the ease of the fallee falling is very much dependant on the force with which the subject hits. The implication you are making is a constant force between the short man and the tall man scenario. DO you think the force is constant like this empirically across most situations?

However psychologically "fighting" is more about a relationship between the two fighters than let's say a concentration on the recipient of a shove or a punch.

15. Apr 3, 2017

### Drakkith

Staff Emeritus
I'm not convinced that it's more difficult to knock over a tall person than a short person. People aren't static objects and that makes it vastly more complicated to get an accurate answer.