1. The problem statement, all variables and given/known data A passenger train is travelling at 29ms^-1 and a freight train is travelling 360m ahead of it at 6ms^-1 in the same direction on the same track. The driver of the passenger train has a reaction time of 0.4s before he starts decelerating. What is the minimum deceleration to avoid colliding with the freight train? 2. Relevant equations x-0=29t+0.5at^2 0=29+at x-350.8=6t 3. The attempt at a solution I tried solving this as follows but my answer is wrong according to a solution I found online. Where am I going wrong? First I calculated that when the driver starts decelerating, the seperation of the trains will be 350.8m. I then let the initial time be this point in time (ie when they are 350.8 apart) and I let x=0 at t=0. So initially, the passenger train is at x=0 and the freight train is at x=350.8. I let the time they meet be t and the displacement of both trains be x at this time. Also, the minimum deceleration would be if the passenger train stops exactly when they meet. Based on this, I got the following equations: For the passenger train we get two equations: x-0=29t+0.5at^2 0=29+at (since it comes to a stop when they meet) For the freight train: x-350.8=6t Solving these, I got a=-0.703, however the solution I found online (in a pdf document of solutions to the problems in Tipler/Mosca 5th edition; this problem is chapter 2 q96) gives -0.754.