Question

a car moving at velocity 72km/h .Suddenly breaks are applied so as to stop the car at a distance 10m find acceleration

Answer 1

speed =72km/h
actual speed=5/18×72=20
time =distance/speed=20/10=2

Answer 2

given:
u =72km/hr=20 m/s
v=0m/s
s=10m
a=?

from 3rd equation of motion we get :
v^2=u^2+was
(0)^2=(20)^2+2×a×10
0=400+20a
-400=20a
a=-20m/s^2. (ANSWER )