We describe our work on qualitative physics for modelling movable objects in Twilight City, a virtual environment for Military Operations on Urbanized Terrain (MOUT). Movable objects such as chairs, boxes, bottles, etc. are quite common in real life. However, the computational cost will be high if the exact physics laws are used to model the behaviour of these objects. To reduce the computational cost of simulating moveable objects in Twilight City, a framework for qualitative behaviour simulation has been proposed and integrated into our simulation engine. Example results show that the proposed framework is successful in modelling the dynamic behaviour of various movable objects in Twilight City in terms of human players? perceptions and responsiveness of the system.