Answer:
[tex]v_{f}=63\ \frac{m}{s}[/tex]
Explanation:
[tex]v_{f}=v_{i}+a\cdot t[/tex]
[tex]v_{f}=15\ +\ 6\cdot8[/tex]
[tex]v_{f}=63\ \frac{m}{s}[/tex]
Therefore, the speed of the car is 63m/s after 8 seconds while accelerating at it maximum capability.