$\left[t_1,t_2\right]$

$\left[0,1\right]$

$\left[1,2\right]$

$\left[0.5,1\right]$

$\left[1,1.5\right]$

${\overline{v}}_i\left(i=1,2,3,4\right)$ (m/s)

${\overline{v}}_1=1.60$

${\overline{v}}_2=-8.2$

${\overline{v}}_3=-0.85$

${\overline{v}}_4=-5.75$