Nobody ever teaches me how physics works

[Aerith's Knight]

In the example 20 N·s-> 10 N·s -> , the object behind the object in the front strikes the object in the front, but with momentum 10 N·s
Why does this happen?

Objects traveling at a constant speed are in force equilibrium. Thus if there is no resisting force (air friction, tire friction, etc), there is no force on the particle, and even if there was the forces working in opposite directions, assuming they are equal would still create zero resulting force (definition of constant speed). So if you are looking at a collision between those two particles, it is no different if they are 20 / 10 or 10 / 0 N.s

The first part i can't explain any different that a simple force balance with non-deforming particles.

Does it have something to do with inertia? Being that the force of inertia on the object with N -> 20 has more inertia that overpowers the N->10 ? I think you're asking why the opposing force ends up being transferred between the objects. I think it has something to do with inertia.

Physics fail. ASL?

Yes physics fail. I want to know why if I push against an object the force doesn't push back at me, or gets transferred to a power plant in brasil. "because that's how it works" ?

It doesn't exactly push back at you. If you push against a cabinet for example, and it doesn't give (no movement), the force pulling back at you, is here then the gravity working on the cabinet and the friction between the bottom of the cabinet and the floor. The reason it "pushes back at you" is because that friction force transfers through the material stiffness to your contact plane. If it was deformable, the force would in fact result in material deformation, instead of "pushing back".

Sorry if my explanation isn't really.. yeah. It's hard to explain things.