JEE Main & Advanced JEE Main Paper (Held On 19 May 2012)

  • question_answer
    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.     JEE Main  Online Paper (Held On 19  May  2012)

    A) \[\frac{u+v}{2}\]                             

    B)                        \[\frac{1}{2}\sqrt{{{u}^{2}}+{{v}^{2}}}\]

    C)                        \[\sqrt{uv}\]                                     

    D)                        \[\sqrt{\left( \frac{{{u}^{2}}+{{v}^{2}}}{2} \right)}\]

    Correct Answer: D

    Solution :

                    Let ?S? be the distance between two ends ?a? be the constant acceleration As we know \[{{V}^{2}}-{{u}_{2}}=2aS\]or\[aS=\frac{{{V}^{2}}-{{u}^{2}}}{2}\] Let V be velocity at mid point. Therefore, \[V_{c}^{2}-{{u}^{2}}=2a\frac{S}{2}\] \[V_{c}^{2}={{u}^{2}}+aS\] \[V_{c}^{2}={{u}^{2}}+\frac{{{V}^{2}}-{{u}^{2}}}{2}\] \[{{V}_{c}}=\sqrt{\frac{{{u}^{2}}+{{v}^{2}}}{2}}\]


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