Place the ball at the top of the path provided and allow it to roll. Observe if the ball crosses all the peaks. If not, vary the initial position of ball.

What did you observe? 
Only at particular initial position, the ball gets sufficient energy to cross all the peaks.

The science behind it :
If you keep the ball at a higher position, more potential energy is stored in the ball, which is turned into kinetic energy when released. At a particular position, the ball crosses all the peaks. When we keep the ball at a very high level, the kinetic energy increases and leads to generate excessive centrifugal force due to which the ball falls out.