1. The problem statement, all variables and given/known data The force required to compress an imperfect horizontal spring an amount x is given by F = 150x + 12x^3, where x is in meters and F in newtons. If the spring is compressed 2.5m, what speed will it give to a 3.5kg ball held against it and then released? 2. Relevant equations Not sure all these are relevant, but... F = ma a = dv/dt K = mv^2 /2 3. The attempt at a solution I made many attempts and the computer told me that none were right. Thanks!