AP EAPCET 23-Aug-2021 Shift 2 Paper

Given, length of train, l=100m
Time taken by an object to cross the train, t=7.2s
Velocity of object opposite to train, v0=5‌km‌h−1 =

25

18

m∕s=1.39m∕s
Let the velocity of train, vt=v
Using the concept of relative motion.
Relative velocity of train w.r.t object vrel=v1+v0
Now, l=vrel×t
100=7.2(vt+v0)
⇒100=7.2(v+1.39)
⇒v=12.5m∕s=45‌km‌h−1