Question

A train 200 m long is running at the speed
of 75 kmph crosses the bridge in 30 sec. the
length of the bridge is ? ​

Answer 1

Answer:

Relative Difference : Distance1 - Distance2 = 20 km

Speed1 - Speed2 = 5km/hr

So, Time = Distance/Speed

= 20km/5

Time = 4 hrs.

Now, Distance is equal to Speed x Time.

(30km/hr + 25km/hr)*4

= 55*4

Ans = 220 km.

Answer 2

Answer:

The speed of a 200m long train is 75 km/h, It crosses a bridge in 30 sec, the length of the bridge  is $424.9m$

​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 quest

length of the train $l=200m$

assume that the length of the bridge is x

time taken to cross the bridge  $t=30s$

speed of the train $V=75km/h=75*5/18=20.8m/s$

but speed is the total distance divided by time

total distance =length of the train +length of the bridge

⇒

$V=x+l/t$

$20.8=\frac{x+200}{30}$

$624.9=x+200\\x=624.9-200=424.9m$

so the length of the bridge $x=424.9m$