I have always though of three basic ways that force fields function.

The first way is that the force field projects an indestructible shell that oncoming objects can never break. Further, the velocity of the oncoming objects is irrelevant. In this case, the rock harmlessly rolls off. 

![Force Field One](https://i.stack.imgur.com/QfE5I.gif "Made in Blender 3D.")

The second way is that the force field applies a force to the oncoming objects accelerating them in the opposite direction. In this case, the rock is slowed down and then repelled by the force field. 

![Force Field Two](https://i.stack.imgur.com/7jFrK.gif)

The third way is that the force field projects an ultra-powerful wall of doom that instantly annihilates any oncoming object. This model uses immensely more energy than the first two.

![Force Field Three](https://i.stack.imgur.com/i6rYt.gif)

My question is: 

What is the most physically accurate model for a force field and which one would be best fitted for protecting a basic human civilization? If none of these types are realistic, are there any other ways one could work?