Question

A train travelling at 79 km/h crosses a man, going in the same direction at 7 km/h in 12 seconds. If the
same
train crosses a woman coming from the opposite direction. in 10 seconds, then the speed (in km/h) of the
woman is​

Answer 1

Step-by-step explanation:

A train travelling at 79 km/h crosses a man walking with a speed of 7 km/h, in the same direction, in 12 seconds. If the train crosses a woman coming from the opposite direction in 10 seconds, then what is the speed (in km/h) of the woman?

We add two speeds when in opposite direction and subtract when in same direction.

Here man and train are travelling in same direction so

Relative speed S1= 78 kp/h - 7 km/h =71 km/h

Convert it to m/s …..multiply it by (5/18)

So ….S1 = (71 x 5) / 18 = 19.7m/s

Here Speed S1= 19.7 m/s , Time (T1)= 12 secs , Time (T2)=10 secs , Distance i.e. Train Length D = ?

We know Distance (D) = Speed (S1) x Time (T1)

D= 19.7 × 12

=236.4m……..Train length

Now train is moving in opposite direction of the women so

D = Speed (S2) x Time (T2)

236.4= S2 x 10

S2= 23.6m/s ……….Relative Speed S2

Convert it to km/h …..multiply it by (18/5)…

(18/5) x 23.6 = 84.96 km/h………Relative Speed S2

Now , Relative Speed S2 = Train Speed + Speed of women

84.96 km/h = km/h + A……………….Speed of women =A

A=10 km/h.

Finally, speed of the women is 10 km/h.