Question

a train 250 m long passes a pole in 10 seconds and a bridge in 25 seconds find the length of the bridge

Answer 1

For pole :-

Time = 10 seconds

Distance = 250m (since it crosses the pole)

Speed = Distance/time

Speed = 250/10

speed = 25m/s

Now in case of bridge

t = 25seconds,

Speed = 25m/s

Distance = length of train + length of bridge

Also, distance travelled = Speed × time

=> 25 × 25 = 625metre

But we know that distance = length of train + length of bridge (since the train crosses the bridge, its own length will also be added to get distance)

=> 250 + length of bridge = 625

=> length of bridge = 625 - 250 = 375m

Length of bridge is 375m

Hope it helps dear friend ☺️✌️

Answer 2

●WHEN A TRAIN CROSSES A POLE●

○THEN○
■distance=250 metre
$because \: when \: the \:end \\ \: point \: of \: train\: reaches \\ \: the \: pole ..\: it \: has \\ \: covered \: a \: distance \\ \: of \: 250 \: metre \: forward$
■time=10 seconds
$given$
■speed=?
speed=distance/time
speed=250/10
speed=25m/s



●WHEN THE TRAIN CROSSES THE BRIDGE●


○THEN○
■distance=250metre+length of bridge
$because \: first \: the \: train \\ \: will \: cover \: the \: distance \\ \: of \: the \: bridge \: and \: then \\ the \: distance \: of \: itself$
let length of bridge be x
distance=(250+x)metre

■time=25 seconds
$given$

■speed=25 m/s
$found \: above$

so the distance is
speed×time
=25×25
=625 metre

BUT TOTAL DISTANCE = (250+x)metre
so
250+x=625
x=625-250
x=375metre

HENCE THE LENGTH OF THE BRIDGE IS 375 METRE.



$hope \: helps$
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