A train is moving on a straight track at 72kmh−1. The driver sees an obstacle 400m ahead and applies the brakes so that the retardation is uniform.
(i) Determine the minimum retardation needed to stop the train just before reaching the obstacle.
(ii) Find the time taken for the train to come to rest under this retardation.
a. (i) Minimum retardation
b. (ii) Time to stop