Constant speed when free-falling... Why??

I’m starting with Unity. I’m trying to implement the jump behaviour for my character, which is a RigidBody. The problem that I am encountering is that the rigidBody falls with constant speed, instead of it being increased with time as it falls. I mean, it is completely constant.

What I would like to do is a simple and typical jump. In this type of jump, the subject starts going up with the same speed that it will have in the moment of landing (supposing that the starting and finishing points are the same).

Thanks!

Okay, I think I’ve discovered why this is happening: my game object is actually a sprite. So, since Unity makes all calculations based on the object’s size (Unity - Manual: Rigidbody component reference - “Use the right size”), and a sprite is actually two-dimensional and doesn’t have volume, I assume that Unity can’t properly calculate the physics stuff with such an object.