A train slows down from 108km/hr with a uniform retardation of 5m/s. How long will it take to reach 18km/hr and what is the distance covered
You mean a = -5 m/s^2
108,000 meters / 3600 seconds = 30 meters / second
18,000 / 3600 = 5 m/s
v = Vi + a t
5 = 30 - 5 t
5 t = 25
t = 5 seconds
x = Xi + Vi t + (1/2) a t^2
x = 0 + 30 (5) - (5/2)(25) = 150 - 62.5 = 87.5 meters