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Matter In Our Surroundings

Question
CBSEENSC9005704

A 100 m long train crosses a 300 m long bridge at a speed of 90 km/hour. How much time will it take to cross the bridge completely?

Solution

Length of the train = 100 m
Length of the bridge = 300 m
Distance covered in crossing the bridge completely is, 
Distance space covered space in space crossing space the space bridge space completely comma space

space straight s space equals space Length space of space train space plus space Length space of space bridge space equals space 100 space plus space 300 space equals space 400 space straight m

space straight v space equals space 90 space km divided by straight h space equals space fraction numerator 90 space cross times space 1000 over denominator 3600 end fraction space straight m divided by straight s space equals space 25 space straight m divided by straight s
therefore space space Time space required space to space cross space the space bridge space is space straight t space equals space straight s over v space equals space 400 over 25 space equals space 16 space straight s.