For this case we have that the final speed is given by:
[tex] vf = a * t + vo
[/tex]
Where,
a: acceleration
vo: initial speed
t: time
Clearing the time we have:
[tex] t = \frac{vf - vo}{a}
[/tex]
Substituting values we have:
[tex] t = \frac{0 - 28}{- 6.4}
t = 4.375
[/tex]
Answer:
it takes 4.375 s for the car to stop
