Define physical model.

Physical models are of two types, static and dynamic. Static physical model is scaled down model of a system which does not change with time. An architect before constructing a building, makes a scaled down model of the building, which reflects all its rooms, outer design and other important features. This is an example of static physical model. Similarly for conducting trials in water, we make small water tanks, which are the replica of sea, and fire small scaled down shells in them. This tank can be treated as a static model of sea.

Dynamic physical model are ones which changes with time or which are function of time. In wind tunnel, small aircraft models (static models) are kept and the air is blown over them with different velocities and pressure profiles are measured with the help of transductions embedded in the model. Here wind changes with time and is the example of dynamic physical model.