You can do a simple inertia experiment to demonstrate this. You'll need a hard-boiled egg and a raw egg for this activity. First, spin the hard-boiled egg on its side. When it's going fast, gently put your fingers down on it to stop it and then move your hand off immediately when it stops. Next, spin the raw egg. Stop it in the same way you did with the hard-boiled egg. After you let go, what happens? The egg should start to turn again. This is because the motion of the liquid within the egg is still going; the force you exerted was not enough to stop both the inertia of the shell and the inertia of the liquid inside of it. If you held the egg longer, enough force would have been exerted to stop the egg completely.
The results of the experiment fit in with the Law of Inertia: an object will continue to remain in one state until sufficient outside force acts upon it, either to put it in motion or to bring it to rest.