relative speed=60km/hr

time takem to cover 60km by two trains is 60/60= i hr

since speed of bird is 60 km/hr therefore distance covered bysuppose the   bird in 1 hr is 60 km ans to 1st part.

consider vel of 1 train to be 60 and other to be zero and suppose it is at distance x from fly

so let the come to the moving trainin time t

d of trian 60 t and d of bird also 60t adding both =120t

so t=sum of both(x)/120t and so dist of bird =60/120*x=x/2and in2nd 3 rd and thus n trips distance of car from fly would be (1/2)raise to power n-1 so trips would be infinite