A4.2 kg block is initially at rest on a horizontal frictionless surface when a horizontal force in the positive direction of an x axis is applied to the block. the force is given by , where x is in meters and the initial position of the block is x = 0. (a) what is the kinetic energy of the block as it passes through x = 3.1 m? (b) what is the maximum kinetic energy of the block between x = 0 and x = 3.1 m