Acceleration Vector (Problem 29)

The position of a particle for t > 0 is given by $\vec{r}(t)=(3.0t^2\hat{i}-7.0t^3\hat{j}-5.0t^{-2}\hat{k})\text{m}.$ (a) What is the velocity as a function of time? (b) What is the acceleration as a function of time? (c) What is the particle’s velocity at t = 2.0 s? (d) What is its speed at t = 1.0 s and t = 3.0 s? (e) What is the average velocity between t = 1.0 s and t = 2.0 s? Select the answer to part (d).