Question

A man is standing on a railway bridge which is 180m long. he finds that a train crosses the bridge in 20 sec but himself in 8 sec. find the length of the train and its speed

Answer 1

The lenth of the train is180 m and the skeed is20 seconds

Answer 2

Answer:

A man is standing on a railway bridge which is 180m long. he finds that a train crosses the bridge in 20 sec but himself in 8 sec, the length of the train is $120m$ and its speed is $54km/h$

Step-by-step explanation:

• The speed (V) of a body is the distance(d) covered by it divided by the time taken (t) to cover the distance

        $V=d/t$

From the question, we have

time taken to cross the man $t'=8s$

the length of the train is the distance crossed, let it be x

⇒the velocity of the train $V=x/8$ (equation 1)

length of the bridge $l=180m$

so total distance covered is $x+180$

time to cross this distance is $t=20s$

the velocity of the train $V=\frac{x+180}{20}$ (equation 2)

velocity is same

⇒$x/8=\frac{x+180}{20}$

$20x=8x+180*8\\12x=180*8\\x=120m$

length of the train $x=120m$

speed of the train

$V=x/8=120/8=15m/s\\V=15*18/5=54km/h$