AFCAT Model Paper 2

GIVEN:
A train running at the speed of 54 km/h crosses a man running in opposite direction in 36 seconds.
Length of the train is 720 meters.
FORMULA USED:
Relative speed = (a + b) for opposite directions
Relative speed = (a – b) for same directions.
Speed = Distance/Time
CALCULATION:
Speed of train = 54 km/h
⇒ Speed of train = 54 × 5/18 = 15 m/s
Suppose the speed of man is x m/s
When the man is running in the opposite direction of train:
Relative speed = (15 + x) m/s

720

(15+x)

=36
⇒ x = 5
⇒ Speed of man = 5 m/s
Now,
When the man is running in the same direction as that of train
Train will cross the man in

720

(15–5)

= 72 seconds
∴ Required time is 72 seconds