For train A, the initial velocity,
u = 54 kmh-1 = 54 ร {5\over18}= 15 ms-1
Final velocity, v = 0ย ย ย and time, t = 5s
For train B, u = 36 kmh-1 = 36 x{5\over18} = 10 ms-1
v = 0;ย ย t =10 s
Speed-time graph for train A and B are shown in the figure.
Distance travelled by train A
= Area under straight line graph RS
= Area of ฮORS
= {1\over2} x OR x OS
= {1\over2} x 15ms-1 x 5s
= 37.5 m
Distance travelled by train B = Area under PQ = Area of ฮOPQ
={1\over2} x OP x OQ
={1\over2} x 10ms-1 x 10s = 50m
Thus, train B travelled farther after the brakes were applied.