Question

brakes are applied to a train travelling at 72km/h after passing over 200m velocity is reduced to 36 km/h find the retardation in m/s

Answer 1

We have, initial velocity=72km/h
Final velocity=36km/h
Distance covered in that time = 200m = 1/5km
To find the retardation, we will use the 3 equation of motion which is v^2-u^2=2as
(36)^2-(72)^2=2×a×1/5
(36-72)(36+72)=2a/5
-36×108=2a/5
-3888×5/2=a
so, a=-9720m/s^2
The retardation is 9720m/s^2