Problem 6. The position function of a particle is t2 t2 r(t) = (431:5 f 4t>. 2 2 When is its speed a minimum? (Hint: the minimum of a one variable func- tion t) is attained at points where f'(t) : 0). Problem 7. True of False? Please motivate your answers. (a) Assume a particle has trajectory r(t), velocity v(t), and acceleration a(t). Then (1 E (r(t) >