Physics for 2D and 3D in Unity are very similar, because they use the same concepts like Ias rigidbodies, joints, and colliders. However, Box2D has more features than Unity's 2D physics engine. It is not a problem to mix 2D and 3D physics engines (built-in, custom, third-party) in Unity. So, Unity provides an easy development way for your innovative games and applications.

If you need to develop some real-life physics in your project, then you should not write your own library, framework, or engine, except specific requirements. However, you should try existing physics engines, libraries, or frameworks with many features already made.

Let's start our introduction into Unity's built-in physics engine. In the case that you need to set your object under Unity's built-in physics management, you just need to attach the Rigidbody component to this object. After that, your object can collide with other entities in its world and gravity will have an affect...