Question

15. Two trains 105 m and 90 m long run at the
speeds of 45 km/h and 72 km/h respectively
in opposite directions on parallel tracks. How
much time do they take to cross each other?
(a) 5s (b) 6 s (c) 7 s
(d) 8 s​

Answer 1

Answer:

6 seconds

length of 1st train 105 m

2nd train 90m

total speed 45+72=117km/h (we add because when it will cross both of the speed will act at same time) known as relative speed

then we will convert it to m/sec

177 × 1000m/3600=177 ×5/18=32.5m/sec

then we will add both length 90+105=195

time taken=

195/32.5m/sec =6 sec