1. The problem statement, all variables and given/known data A body of mass 5 kg is acted on by a force in a straight line. The magnitude of the force after t seconds is given by (2t - 3t^2) kg wt. If the body has an initial velocity of 3ms-1 in the same direction as the force, calculate its velocity after 4 seconds. 2. Relevant equations ∑F = ma a = dV/dt 3. The attempt at a solution So what I've done is this. m = 5 F = (2t - 3t^2) a = (2t - 3t^2) / 5 dV/dt = (2t - 3t^2) / 5 v = ∫(2t - 3t^2) / 5 dt v = (t^2 - t^3) / 5 + c Using t = 0, v = 3 (from initial velocity), solving for c yields c = 3. So, v = (t^2 - t^3)/5 + 3 and substituting t = 4, I get v = -6.6ms-1 The back of my textbook gives an answer of -91.08ms-1, could someone please tell me where I've gone wrong?