Okay, I got another problem for you guys that I have been trying to figure out. Here first is the diagram: I have been experimenting with different weights of balls and different weights of cars, also different ramp lengths. 5 balls are supposed to be used. Nothing seems to work at all. I am wondering if it is even physically possible now. The only time I can get it to work is if I propel the car by giving it a push first, but that is not the object of the car. It is supposed to be propelled by the weight of the balls pushing the car as they are rolling down the incline. Once they have rolled off of the ramp, due to the momentum of the car compared to the momentum of the ball the first couple should backwards in the opposite direction of the car, but then as the car goes faster, it should impart a greater momentum on the remaining balls on the cart therefore the later ones after rolling off of the cart will move in actually the same direction as the cart is travelling. What do you guys think is this possible to recreate? Or is it only theoretically possible, or just plain impossible without the help of outside forces? Thanks ahead of time for any help.