[填空题]
A particle moves in a s gthvgj -8.j(otz8hvqi s* :6jt6xs+g3ye ,c jvraight 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.
