A 100, m long train is moving with a uniform velocity of 45, km/hr . time taken by train to cross a

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2.Motion in Straight Line

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A $100\, m$ long train is moving with a uniform velocity of $45\, km/hr$. The time taken by the train to cross a bridge of length $1 \,km$ is.........$s$

A

$58$

B

$68$

C

$78$

D

$88 $

Solution

(d) Length of train $= 100\,m$

Velocity of train$ = 45\;km/hr = 45 \times \frac{5}{{18}} = 12.5\;m/s$

Length of bridge $= 1 \,km = 1000\, m$

Total length covered by train $= 1100 \,m$

Time taken by train to cross the bridge $ = \frac{{1100}}{{12.5}}= 88 \,sec$

Standard 11

Physics

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