Shortcuts and delays
Two marbles race against each other with the starting blocks and finishing tape at the same place, but differing in the distance travelled and the gradient of the track. In the arc-shaped track the marble accelerates rapidly.
The steep gradient means that the marble falls almost in free fall with respect to the acceleration it experiences. The track then becomes flatter, but the high speed that the marble reached at the start means that it reaches the finish before the marble with the shorter distance to travel, the short-cut.