# Physics asset Mass, physics material density and other not work?

I have a constraint between two bones, with a linear limit and certain applied forces. Adjusting the body mass in kilograms, adjusting the density of the physical material or any other aspect gives totally random results, regardless of the density or weight, the behavior is unexpected, adjusting the density to a lower value results in a heavier object , setting it higher results in a light object, no matter how the values ​​move, the scale of the mass does not matter either, the result always varies between two behaviors and no other, no matter how I adjust it, I always get the same. Only two results.

What is happening here exactly? All this happens when it is a physical asset

According to the physx documentation, the force that is applied to push or pull between two bodies joined by a physical constraint is calculated based on mass, so a low-mass object cannot lift a higher-mass object. This can really break anyone’s mind for a long time. So you should always take this into account by limiting complex and simple forms a lot, causing all kinds of counterintuitive behaviors.