Explanation:
initial velocity= 80km/hr = 22.22 m/s
distance= 40m
Final velocity= 0m/s ( as it needs to be stopped)
Using third equation of motion,
=> 2as = v² - u²
=> 2a * 40m = 0² - (22.22 m/s)²
=> a = - 493.72/80 m/s²
=> a = - 6.17m/s²
Using first equation of motion,
=> a = v - u /t
=> -6.17 = 0-22.22/t
=> t = -22.22/-6.17 s
=> t ≈ 3.7 s = stopping time
