The equation of motion of a particle is $s = t^3 - 3 t,$ where $s$ is in meters and $t$ is in seconds. Assuming that $t \ge 0,$ answer the following questions.

1. Find the velocity $v$ as a function of $t.$
Answer: $v(t) =$

2. Find the acceleration $a$ as a function of $t.$
Answer: $a(t) =$

3. Find the acceleration after $2$ seconds.
Answer (in $\text{m/s}^2$): $a(2) =$

4. Find the acceleration when the velocity is $0.$
Answer (in $\text{m/s}^2$): $a =$