Question

Two trains , each having a speed of 30km/h, are headed at each other on the same straight track . A bird that can fly 60 km/h flies off the front of one train when they are 60 km apart and heads directly for other train . On reaching the other train , the bird flies directly back to the first train and so forth . What is the total distance the bird travels before the trains collide ?

Answer 1

assuming trains A and B (keeping b at rest)
Vab = Va -Vb
=30km/hr
2(Aab)(Sab)
${v}^{2} - {u}^{2} = 2as$
v=0
u=30
s=60

using this we get Aab = 7.5
now time t
v=u+at
0=30+(7.5)t
we get t=4
so bird will travel distance d=vt
d=60*4
240 km