We will teach you to make a realistic ball rolling down the hill using Blender's game engine.
First, make a plane. Subdivide it a few times and scale it up a lot. Now, make a sphere. It can be any kind except meta. With the sphere selected, go to the game engine settings. (It is the little purple Pacman-icon.) You will see something that says Actor. Press it. Now press Dynamic. You will see a bunch of settings available now. Change Size to 1.4. Also enable Rigid body. This will let the ball roll. Edit the plane, pulling vertices up or down. For this example, make it look like a canyon. Put the ball at the start point and press the P-Key. You will see the ball fall in, and roll. If it doesn't go the way you wanted, Pull some vertices of the canyon downwards. Incline your plane to let the ball roll. If you just see white, don't worry. Press escape to exit the game mode. Press Z key. Go back into game mode and it will look like wireframe. the ball will roll through the canyon. Well done! You should give it finishing touches, like effects, color, etc. And that's it.