Question

A 100m long train crosses a man travelling at 5 km/hr. in opposite direction in 7.2 seconds then the velocity of train is:-

• A. 40 km/hr
• B. 25 km/hr
• C. 20 km/hr
• D. 45 km/hr

Answer 1

The correct option is D 45 km/hr

Given : $V_M=5$ km/hr

Length of the train $L=100m=0.1km$

Time taken by the train to cross the man $t=7.2$ s $=\frac{7.2}{3600}$ hr

Let the velocity of train be $V_T$ in opposite direction to that of man.

$\therefore$ Velocity of train w.r.t man $V_{TM}=V_T+V_M=V_T+5$ km/hr

Now $L=V_{TM}t$

$\therefore$ $0.1=(V_T+5)\times \frac{7.2}{3600}$ $⟹V_T=45$ km/hr