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roshan-rox | (Level 1) Valedictorian

Posted July 3, 2013 at 12:43 PM via web

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Using this graph or otherwise,

Find the velocity with which and the time at which the front of the train   passed B

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted July 3, 2013 at 1:31 PM (Answer #1)

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The distance traveled can be obtained from the area of the time-velocity graph. As we know when the train passes the post it will travel 100m in 10s. In the graph this region is a trapezoid and its area will be 100.

Area of trapezoid `= (11+V)/2xx10`


`(11+V)/2xx10 = 100`

`V = 9`


So the velocity of train at the start of post is 9m/s.


Using gradient of the graph we can say;

`V/T = 11/(T+10)`

`9/T = 11/(T+10)`

`T = 45s`


So the front of train will pass B after 45 seconds it started travel and with a velocity of 9m/s.


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