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  • A passenger sitting in a train A moving at 90 km/h observes another train B moving in the opposite direction for 8 s. if the velocity of the train B is 54 km/h, then length of train B is : &

A passenger sitting in a train A moving at 90 km/h observes another train B moving in the opposite direction for 8 s. if the velocity of the train B is 54 km/h, then length of train B is :
 

Option: 1

120 m 


Option: 2

200 m 


Option: 3

320 m 


Option: 4

80 m


Answers (1)

best_answer

\begin{aligned} & \mathrm{V}_{\mathrm{A}}=\frac{90 \mathrm{~km}}{\mathrm{hr}}=25 \mathrm{~ms}^{-1} \\ & \mathrm{~V}_{\mathrm{B}}=\frac{54 \mathrm{~km}}{\mathrm{hr}}=15 \mathrm{~ms}^{-1} \\ & \overrightarrow{\mathrm{V}_{\mathrm{BA}}}=\overrightarrow{\mathrm{V}_{\mathrm{B}}}-\overrightarrow{\mathrm{VA}}=40 \mathrm{~ms}^{-1} \\ & \text { Time of crossing }=\frac{\text { Length of train }}{\text { Relative velocity }} \\ & 8=\frac{\ell}{40} \\ & \ell=8 \times 40=320 \text { meter } \end{aligned}

Posted by

Pankaj Sanodiya

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