Answer
At the bottom of the track, a heavier car has a greater fraction of its energy in the form of translational kinetic energy which means that it will be moving faster than lighter cars.
Work Step by Step
At the top of the track the car has a certain amount of gravitational potential energy that is proportional to the car's mass.
At the bottom of the track, this energy has been converted into translational kinetic energy of the car and rotational kinetic energy of the wheels. The fraction of the initial energy that is converted into rotational kinetic energy will be smaller if the mass of the car is greater.
Therefore, at the bottom of the track, a heavier car has a greater fraction of its energy in the form of translational kinetic energy which means that it will be moving faster than lighter cars.
