Set up the looped track on a completely level surface. Set up the photogate at the beginning of the loop. Start the ball with an arbitrary initial velocity. Use this velocity, the mass of the ball, and the acceleration due to gravity to determine centripetal accelerations at distinct points along the loop (especially the top).
Did the ball remain on the track for the whole loop? Did it fall? Why?
Repeat this with spheres of different weights. Do they require a different velocity to remain on the track? Explain.