The position of a particle is given by ` vec r= 3.0 t hat i - 2.0 t^2 hat j + 4.0 hat k m`, wher (t) in seconds and the coefficients have the proper units for ` vec r` to be in metres. (a) Fing the ` vec v` and ` vec a` of the particle ? (b) What is the magnitude and direction fo velocity of the particle at ` t= 2 s`?