The loop-the-loop apparatus can be used to study the projectile motion in a rather unusual way. If the rolling ball, used in this classic demonstration, does not have enough energy to make the loop, it will fall from the track starting at some point P, corresponding to an angle q.
See for example this "stroboscopic" photo for the case q = 30 degrees.
The previous picture actually comes from the following movie, for the case q = 30 degrees.
Here are similar movies, for other interesting cases:
For q = 45 degrees.
For q = 60 degrees.
Want to know more about all this? Please check out my paper "The Projectile inside the Loop," published in Physics Education.