When the ship�s hit by phasers from another ship, it shakes a lot. So that�s not the same principle�

Well it is the same principle, ultimately. We do see on Star Trek, for example, the ship will get involved in a tussle with a alien and will be fired upon, and the ship shakes. Well, if we have inertial dampers how come the crew is feeling that shake? Presumably the inertial dampers have a certain response time. It�s not instantaneous, so there�s a little bit of a lag and it�s that lag that creates the shake that we momentarily experience when the ship is hit by phaser fire or a photon torpedo or something.