The physics in the Homeworld Universe appear to be a mix of the real Laws of Physics and an exaggerated physics, intended to compromise between believability and the entertaining dogfighting behavior of other space operas, such as Star Wars. It is quite possible to reintroduce a more realistic physical behavior with some modifications to the game files.
Ships do not seem to exist in a frictionless space, for example, instead they slow down and come to a halt when their engines are cut, instead of floating in a straight line. Also, ships seem to accelerate almost equally fast in all directions, despite having only rear-facing main engines and only smaller maneuvering thrusters which are only apparent on the ships' textures.
There are, however, a few examples of the real Laws of Physics in the Homeworld Universe. For example, ships do not immediately go really fast the second they hit the thrusters. Instead, they have to sustain a trajectory to be able to go at faster speeds. Ships generally follow an authentic, although simplified physics model and will react to accelerating forces (from thrusters or collisions) according to the magnitude of that force and their mass. Vessels hit by kinetic rounds will be thrown off course and pushed back according to the mass of the bullet, and colliding ships will bounce off each other according to their relative speeds and masses (unless collision damage becomes a factor).
Initially the developers of the game intended to make visible exhaust for these smaller jets. It was also intended to differentiate between accelerated flight and unaccelerated "cruising" by altering the appearance of the ships' ion trails. These details were later cut for gameplay or budgetary reasons and not reintroduced in the sequels.