I subscribe to the KISS principle especially when showing something that is new, and the concept of inertia is like that.
The key concept is the natural state of affairs in the world is that objects have a constant velocity unless you do something to them. So an object at rest will remain so, and an object in motion will continue with that same motion unless it interacts with something else.
So roll a bowling ball, what happens, it keeps moving at essentially the same velocity until it hits the pins. Put a book on the table. You can watch it for a very long time but it won't move. Imagine you are in a car not wearing your seat belt, and someone puts on the breaks. You feel like you have been pushed forward, but what is happening is the car is slowing down but your body continues moving and you smash into the dashboard.
Those are illustrations, but you asked for an experiment. That depends to some extent on the grade level of the students, so I would need that information.