I always rationalized the “truck/car smashes around me” as a corollary of their (Superman/Supergirl) flight powers: instead of movement (flight) they would fix themselves to a point of reference (i.e. the road).
Unfortunately most of the other intersections of super-strength and physics I find to be immersion breaking. I will admit I can put up with a fair amount of unintentional reality twisting before it becomes an issue but when they get it right (rarely) makes it that much sweeter.
