[填空题]
A particle moves along a r665-fnqbusuzt n.. n strai 9v toxa,ag5he7 4s8wjght line so that its velocity, $v \mathrm{~ms}^{-1}$ , after t seconds is given by $v(t)=1.5^{t}-4.9$ , for $ 0 \leq t \leq 6 $.
1. Find when the particle is at rest.
2. Find the acceleration of the particle when t=3 .
3. Find the total distance travelled by the particle.
