The pine car starts from a stationary slope and then runs to the horizontal track. According to the principle of energy conservation, the horizontal speed of the pine car depends on its own mass and initial potential energy. In the case of similar volume and length, the center of gravity of the pine truck must be placed on the top of the slope, which is the rear of the pine truck, and the heavier the better (but dont make it unbalanced), so add weight to the rear. Weight gain is not about adding bulk or height, but choosing a high-density well-shaped material and grooving the wood so that the tungsten blocks are embedded in the wood itself.