Inclined Plane physics!

Hi,

I didn't find any similar question that matches my needs, so I apologize in advance if the answer is in some topic.

I'm new to unity, and in my project I'm trying to simulate simple physic matters concerning forces on a inclined plane.

I tried to create a ramp using a plane, or a cube with scale like (30;0,1;10), with a 40º rotation over the z axis. I created a small cube, scale(2,2,2), gave it similar rotation and place it on the top of the ramp.

I intend for the cube to slide down the ramp smoothly so than I can calculate it's acceleration speed, etc.

My problem is that the cube don't slide, it starts to stumble on the plane and turns over itself over and over until it hits the ground. I tried box collider and mesh collider on both cube and ramp, and I gave both rigidbody component.

Can anyone point me to the right direction??

Thanks in advance