If deceleration is constant, than our velocity at any time can be calculated by subtracted a*t from our initial velocity.
V = Vi - at
Now if you integrate you get a formula for distance, and your + C we'll just consider as 0.
then the formula for acceleration is
now you need to find the velocity formula
where that is the anti derivative of acceleration
where t is time in seconds and 90 is the inital velocity which in this case C
to show my work
It will have stopped when velocity is 0
so = 0 and solve for t
t = 4.09
no you need to find the distance traveled for this time now you must take the anti derivative of the velocity formula which is
C is in the distance formula for something like this is 0 because C or s(t) sub 0 is usually initial height
so now plug in
t = 4.09
which equals 184.0909 feet
I maybe be totally wrong here
but it takes 4.09 seconds to stop and the car travels a distance of 184.09 feet
If your acceleration is in ft/s/s, than when you integrate, your velocity is in terms of ft/s. Meaning your constant of integration cannot be in mi/h.
Substitute 132ft/s for 90m/h. And do your time and distance calculations again. Everything else you did was right.