It would be nice to have a testbed project that one for all could nail how to use meters as units instead of pixels. It seems those of us who does not have a strong physics background (read: me) have problems to do so.
It's not a physics problem, though
It's fairly "render specific". Here's a potential example: My view of the game is 16m x 12m with a box 2m square inside. My screen resolution is 800 x 600. My scaling factor is thus 50. So, to render the box? Scale its position by 50, and the length of its sides by 50. The physics play out in their safe units, you scale to your desired pixel view.
That's really all it is