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Govind_Balaji
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Homework Statement
A train passes through an electric post in 10 seconds. With same velocity, it passes through a 2km long bridge in 110 seconds.Find the velocity of the train:
a)18kmph b)36kmph c)72kmph d)90kmph.
Homework Equations
The Attempt at a Solution
The train passes through the electric post in 10s. Let it velocity be ##v##.
##\Rightarrow \text{Length of the train} = 10v##
Then I calculated the change in displacement of the train with respect to the bridge when it passes through.
https://www.physicsforums.com/attachment.php?attachmentid=70093&stc=1&d=1401201462
##\text{Displacement of train from bridge after overtake}=2km+10v##
##\text{Displacement of train from bridge after overtake}=-2km##
##\delta s=(2km+10v)-(-2km)=4km+10v##
It took 110 seconds for the train.
Its displacement=##110v##
##\Rightarrow Displacement=110v=4km+10v##
##v=\frac{4*3600}{100}km/h \Rightarrow v=108km/h##
But itsn't in the options.
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