First slide
Relative motion based problems
Question

A train of 150 metre length is going towards east direction at a speed of 10 m/s. A parrot flies at the speed of 5 m/s towards  west direction parallel to the railways track. The time taken by the parrot to cross the train is

Moderate
Solution

Velocity of the train = 

\large \overrightarrow {{V_T}} = 10\widehat i\;m/s

. velocity of the parrot = 

\large \overrightarrow {{V_P}} = 5( - \widehat i)\;m/s


 

\large \therefore

 

\large \large \overrightarrow {{V_P}}

 = velocity of parrot relative to the train = -15

\large \large \overrightarrow {{V_P}}-\large \overrightarrow {{V_T}}=-15\hat im/s


 

\large \therefore t = \frac{l}{{\left| {\overrightarrow {{V_r}} } \right|}} = \frac{{150}}{{15}} = 10\sec .

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