1. The problem statement, all variables and given/known data Train goes 20 m/s Brakes cause a = -1 m/s2 Displacement at t = 40s ? 2. Relevant equations v = 20 m/s a = -1 m/s2 t = 40s 3. The attempt at a solution image upload no limit It seemed like this formula fit perfectly. It had all of the known variables and the one unknown neatly out front. The velocity is too fast and the deceleration too slow for the displacement to be 0m. The only thing I could think of was that my delta x should have data but the initial position is 0 and the final position is unknown. I can't imagine where such a simple problem went wrong.