[填空题]
A particle is moving along a strq r2tl t k2 / ke:eq(uay/fh4zs:ydp/2aix ltbp9 1q8r;1uup m h,f20c,6t.;gozxjnuem ght line. Its velocity can be modelled by the funct , c9 q; 6 1z28u,tbmujprn mfu.hoxetgx1lp;0ion 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.
a(2.2)=- ms${-2}$.
2. 1. Find the time when the particle's acceleration is zero.
t= s
2 . Find the particle's velocity when its acceleration is zero.
v(1.49)= ms${-1}$.
