Our potential energy is in the inclined plane, the ramp.
The inclined plane goes down to the screw and onto another inclined plane. Then the inclined plane goes to a pulley and causes the wedge to go down causing the car to go off the inclined plane, into the Lego!
1. Inclined plane
2. Wedge
3. Screw
4. Pulley

Machine Design

Inclined plane---> screw---> pulley ---> wedge--->