A person 'A' standing in the middle of a platform of length 300m. Two trains respective of lengths 120m and 250m running with respective speeds of 54km/h and 72km/h enter the platform fr opposite ends at the same time (on parallel tracks). How much of the length of train 'C' does the person see while it passes him if train 'B' comes in between him and train 'C' to block his view?
Answers
Answer:
90m according to me..if you have an answer do tell.
Step-by-step explanation:
Converting the speeds of trains B and C to m/s -
train B =15m/s and train C=20m/s.
So obviously train C shall reach the middle of the platform first = 150m. Time taken for it =150/20= 7.5 second ----(i)
Meanwhile in 7.5 seconds train B just covers 15*7.5 distance= 112.5m. And takes 150/15= 10seconds to reach the middle of the platform. (ii)
Therefore person A has clear view of train C for these 2.5 seconds. (ii)-(i)
And train C covers 2.5 seconds*20m/s=50m of its length infront of person A. ---(iii)
Train B to pass person A would have to cover 150m+120m=270m taking 270/15= 18 seconds. Train C would have to cover 150m+250=400m taking 400/20=20seconds.
So there is a 2 second gap here where person A can view train C, therefore 2s*20m/s=40m --(iv)
(iii)+(iv)=90m [50m at the start as train C was faster and 40m at the end as train C was more than double train B's length]