[填空题]
A particle moves in upns-c sx5t,4b/ ohj.hd7x tox11jjbp my839 a straight line with velocity $v(t)=2 t-0.3 t^{3}+2$ , for $t \geq 0$ , where v is in $\mathrm{ms}^{-1}$ and t in seconds.
1. Find the acceleration of the particle after 2.2 seconds.
2. a. Find the time when the acceleration is zero.
b. Find the velocity when the acceleration is zero.
