To conduct this demo, release two balls simultaneously from the high end of the track.
On the high-load road, both tracks have the same starting and ending height, so both lose the same amount of potential energy over the course of the track and end with the same kinetic energy, but they reach the end at the end at different times due to the shape of the track. The "low" ball is greatly sped up at the dip in the track but slows once it reaches the level part to the same speed it would have had as if it had been travelling on the other ("high") track. This demonstration challenges how students think about conservation of energy.