True.
In a roller coaster, if the second hill is bigger than the first hill, the coaster may not have enough potential energy to overcome the height of the second hill after descending the first hill. The initial potential energy at the height of the first hill is converted to kinetic energy as the coaster descends, but if the following hill is higher, the coaster may not have enough kinetic energy to reach the top of the second hill, resulting in it being unable to continue on the track.