Question

A car moving along a straight highway with a speed of 126 km/h is brought to stop with in a distance of 200 m. what is the retardation of the car (assumed uniform) and how long does it take for the car to stop? 

Answer 1

 Initial velocity of car =126 km/h

Answer 2

Speed of car is 126kph = 35m/s

V= 0

S=200 m

0- 35²=2×a x S    (v2=u2= 2aS)

-1225= 400 a

a= - 3.06 m/s2  

retardation= 3.06 m/s2

Time using first equation 

T= v-u/a

T= 35/3.06 ~ 11.2 s