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A train passes an electric post …

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A train passes an electric post in 10 sec. and a bridge of length 2km. in 110 second. what is the speed of the engine?

  • 1 answers

Naveen Sharma 7 years, 5 months ago

Ans. Let Length of Train = x meter

Time taken to cover post = 10 sec

if a train pass post. it mean it is covering distance equal to its length 

So speed = {tex}{distance \over time } = {x\over 10} \ .... (1){/tex}

Again if it pass a bridge it cover distance equal to sum of length of bridge and length of train. 
Length of Bridge = 2 Km = 2000 m

So distance covered =  ( 2000 + x ) m 
Time taken = 110 sec 
So Speed = {tex}{2000+x\over 110 } \ ........... (2){/tex}

From (1) and (2), we get

 {tex}=> {x\over 10}={2000+x\over 110}{/tex}

=> 110 x = 20000 + 10 x

=> 100x = 20000

=> x = {tex}{20000\over 100} = 200 \ m/s{/tex}

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