The question’s motivation is really vague but I like theory so…You have 2 broad options here depending on your scale and vision:
- Add physical colliders to prevent your physical objects flying off. (invisible walls and such)
- Don’t use physical objects but actors that move on the navmesh and simulate the physics yourself.
Approach 2, of course is only feasible if you only need simple physics and have few “pseudo-physical” objects.