Question

A train 150 m long is moving with a speed of 90 km/h. In what
time shall it cross 850 m long bridge ?​

Answer 1

$\huge\underline{\underline{\bf \orange{Question-}}}$

A train 150 m long is moving with a speed of 90 km/h. In what time shall it cross 850 m long bridge ?

$\huge\underline{\underline{\bf \orange{Solution-}}}$

$\large\underline{\underline{\sf Given:}}$

• Lenght of train = 150m
• Lenght of bridge = 850m
• Speed of train = 90 km/h

in m/s

$\implies{\sf 90×\dfrac{5}{18}}$

$\implies{\bf Speed = 25\:m/s }$

$\large\underline{\underline{\sf To\:Find:}}$

• Time at which it cross bridge (t)

✪$\large{\boxed{\bf \blue{Speed = \dfrac{Total\:Distance}{Total\:time}} }}$

$\implies{\sf 25=\dfrac{150+850}{t}}$

$\implies{\sf t = \dfrac{1000}{25}}$

$\implies{\bf \red{Time( t )= 40\:s}}$

$\huge\underline{\underline{\bf \orange{Answer-}}}$

In ${\bf \red{40s}}$ train crosses the bridge.

Answer 2

$\sf \fcolorbox{red}{pink}{ \huge{Solution :)}}$

Given ,

• Length of train = 150 m
• Speed of train = 90 km/h
• Length of bridge = 850 m

In terms of SI unit ,

Speed of train = 90 × (1000/3600) = 25 m/s

As we know that ,

$\large \sf{{ \fbox{Speed = \frac{Distance}{Time} }}}$

Thus , the time required to cross a 850 m long bridge is

Time = (850 + 150)/25

Time = 1000/25

Time = 40 sec

Hence , the time required to cross a 850 m long bridge is 40 sec

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