Ch Resources 50% The position function s(t) = 1512 + 341 models the signed distances from the origin at time r of an object in rectilinear motion. Find the velocity of the object at any time f. (Express numbers in exact form. Use symbolic notation and fractions where needed.) u(t)= Find the acceleration a of the object at any time 1. (Express numbers in exact form. Use symbolic notation and fractions where needed.) a(t) =