Eh, I had a player cast a F6 Physical Barrier in front of a chasing car once, neither side survived. At some point, precise physics are boring and you just make a rough decision.
True.
but a having a grounding in reality is useful. Especially for games like SR where reality is intermixed with fantasy.
To some degree, they do have a barrier chart so you can figure out its relative strength compared to real world objects. 5 is plastlboard which if like plasterboard is super weak, next level up a solid wood door, a chain link fence is 8. Which is sort of weird as I can definitively say you can drive right through a chain link fence but I wouldn't want to drive through a solid wood wall. Though that's more because what holds a chain link fence to a support pole can be weak not the chain link part.
As an aside to the overall discussion spells sort of do need a cast in relation to what you are on effect. If you cast shadow, chaotic world in a plane it being gone instantly is kind of lame. It doesn't thematically fit the world that well and the rules are not intuitive like that. Casting a barrier around you and walking should be a normal thing. All or almost all area sustained spells should have a target a spot or a thing/person option