The motion analysed is that of two balloon-powered cars. Car A (on left), which has a mass of 125g, is lighter than Car B (on right), which has a mass of 175g. This report analyses the motion of the two cars travelling in opposite directions, powered by the balloons, and then colliding with each other.
In phase 1, both cars were accelerating, powered by the balloons. In phase 2, the cars collided, with car A coming to a rest momentarily while car B slowed down. In phase 3, car A started moving in the opposite direction while car B slowed down further. The forces acting on the cars result in the respective motions during the different phases.
Author: video: ClaraKeng, model: lookang
More information at: http://weelookang.blogspot.sg/2014/07/tracker-balloon-propelled-model.html