Kinetic energy is a body that possesses by virtue of being in motion. While potential energy possesses a body by virtue of its position relative to others, stresses within itself, electric charge, and other factors. As the “car” moves along the track its kinetic energy coverts to potential energy when it moves up or down one of the hills. With the initial motion already pushing it when it reaches a slope or dip it uses its own motion to move along the track.
For my track I used cardboard and for my “car” I used a spool of thread. The weight of the cardboard is about .13 kg and the spool is about 0.9
P.s. these were my answers and I got a pretty good grade, for the weight of the track and "car" I did estimate it.