Agolf ball is hit off a tee at the edge of a cliff. its x and y coordinates as functions of time are given by x 5 18.0t and y 5 4.00t 2 4.90t2, where x and y are in meters and t is in seconds. (a) write a vector expression for the ball's position as a function of time, using the unit vectors i^ and j^. by taking derivatives, obtain expressions for (b) the velocity vector vs as a function of time and (c) the acceleration vector as as a function of time. (d) next use unit-vector notation to write expressions for the position, the velocity, and the acceleration of the golf ball at t 5 3.00 s.