The position of a particle moving along the x-axis is given by x(t) = = 4.2 2.5t m. (Assume t is in seconds.) (a) At what time (in s) does the particle cross the origin? 1.68 S (b) What is the displacement (in m) of the particle between t = 3.2 s and t = 6.4 s? (Indicate the direction with the sign of your answer.) -11.8 x m