Question

How is weight distributed when legs are astride?

Answer 1

Is there a simple and quick formula to find the weight (the force acting) on each leg, especially when legs are astride and they are not equally stretched?

(or, better) not equally distant from the center of mass? Can you give a brief description of the principle and formulas involved?

I couldn't find an appropriate picture, but suppose this man here below brings his back foot/leg forward nearer the Center of Mass.

Supposing he weighs 80Kg and is tall 170 cm, given that in a male the CoM is near the sternum, if the feet are equidistant from CM we would have two triangles

1-2) from CM to foot 1m, angle:45°, height (to CM) 71 cm, base 71 cm

In this position can intuitively say that the weight is equally distributed (40-40) on the legs. (or are there other relevant factors to be considered?). But, if

2) the rear leg is moved further forward, then the triangles will not be equal anymore, how do you find out:

the distribution of thw weight on each leg?

the horizontal component of the force that must be counterbalanced by friction?

can we apply the parallelogram to each triangle here?

Is it possible to find just the percentage of the weightdistribution without examining the whole problem and doing a lot of operations?

If you do not wish do use numbers just explain the principles.

You write down the equation that the total forces on all parts of the feet from the floor are equal to the weight of the person; and the total torque r⃗ i×F⃗ i relatively to the person's center of mass is zero

Answer 2

What you want to do is read up on or look into some basics of structural and/or mechanical engineering. And, if you're really interested, finite element methods. The former would be more helpful because stuff like this is basically their specialty and most of what they do. The latter is somewhat helpful because it is good for modelling it on a computer especially when there are even more components to the problem.