Initial velocity,
u = 126kmh-1 = 126 × \(\frac{5}{18}\) ms-1 = 35m-1
Final velocity, ν = 0;
Distance, S = 200m
Using ν2 – u2 = 2aS,
02 – 35 × 35 = 2a × 200
or
a = −\(\frac{35×35}{400}\) ms-2
= 3.06 ms-2
So, the retardation of the car is 3.06 ms-2
Using ν = u + at,
0 = 35 - 3.06 × t
or
3.06 t = 35
t = \(\frac{35}{3.06}\)s = 11.4s.