1. The problem statement, all variables and given/known data I need to find the acceleration, a(t), for which a particle moves on a straight line of a length D. V(0)=0 V(final, that is at x = D) = U a is always positive, but NON-INCREASING!!! What is a(t) for which the particle reaches the end of the line the slowest as possible? 2. Relevant equations Calculus Variational 3. The attempt at a solution Obviously I tried to address it with functional derivative with Lagrange constraints, but I failed.