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Question: Answered & Verified by Expert
A goods train accelerating uniformly on a straight railway track, approaches an electric pole standing on the side of track. Its engine passes the pole with velocity $u$ and the guard's room passes with velocity $v$. The middle wagon of the train passes the pole with a velocity.
PhysicsMotion In One DimensionJEE MainJEE Main 2012 (19 May Online)
Options:
  • A
    $\frac{u+v}{2}$
  • B
    $\frac{1}{2} \sqrt{u^2+v^2}$
  • C
    $\sqrt{u v}$
  • D
    $\sqrt{\left(\frac{u^2+v^2}{2}\right)}$
Solution:
2110 Upvotes Verified Answer
The correct answer is:
$\sqrt{\left(\frac{u^2+v^2}{2}\right)}$
Let ' $S$ ' be the distance between two ends ' $a$ ' be the constant acceleration As we know $V^2-u^2=2 a S$
or, $a S=\frac{V^2-u^2}{2}$
Let $V$ be velocity at mid point.
Therefore, $V_c^2-u^2=2 a \frac{S}{2}$
$$
\begin{aligned}
& V_c^2=u^2+a S \\
& V_c^2=u^2+\frac{V^2-u^2}{2} \\
& V_c=\sqrt{\frac{u^2+v^2}{2}}
\end{aligned}
$$

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