Chapter 4, Problem 16P

GO The velocity $\stackrel{\to }{v}$ of a particle moving in the xy plane is given by $\stackrel{\to }{v}=(6.0t-4.0t^2)\hat{i}+8.0\hat{j}\text{,}$ with $\stackrel{\to }{v}$ in meters per second and t (> 0) in seconds. (a) What is the acceleration when t = 3.0 s? (b) When (if ever) is the acceleration zero? (c) When (if ever) is the velocity zero? (d) When (if ever) does the speed equal 10 m/s?