Write a vector expression for the ball's position as a function of time (in m), using the unit vectors î and ĵ. (give the answer in terms of t.) r = m by taking derivatives, do the following. (b) obtain the expression for the velocity vector v as a function of time (in m/s). (give the answers in terms of t.) v = m/s (c) obtain the expression for the acceleration vector a as a function of time (in m/s2). a = m/s2