Highway crash barrels work by soaking up the force of a collision instead of letting it damage whatever is behind them. This project tests whether cups filled with sand or water can do the same thing. You roll a model car down a ramp into a copper plate, placing the cups in front as a barrier. After each crash, you measure how much the copper plate bends. That bending tells you how much of the impact each filling absorbed compared to an empty cup with nothing inside.