JEE Main & Advanced Sample Paper JEE Main Sample Paper-42

  • question_answer
    Direction: Question based on the following paragraph.
    Two rods 1 and 2 are released from rest as shown in figure.
    Given:\[{{l}_{1}}=4l,{{m}_{1}}=2m,{{l}_{2}}=2l\]and\[{{m}_{2}}=m.\]There is no friction between the two rods. If \[\alpha \]be the angular acceleration of rod 1 just after the rods are released. Then
    What is initial angular acceleration of rod 2 in terms of the given parameters in the question?

    A) \[\left[ \frac{2\sqrt{3}g}{2l}+2\sqrt{3}\alpha  \right]\]          

    B) \[\left[ \frac{3\sqrt{3}g}{l}-\sqrt{3}\alpha  \right]\]

    C) \[\left[ \frac{6\sqrt{3}g}{8l}+5\sqrt{3}\alpha  \right]\]          

    D) \[\left[ \frac{3\sqrt{3}g}{8l}-\frac{8}{\sqrt{3}}\alpha  \right]\]

    Correct Answer: D

    Solution :

    \[{{\alpha }_{2}}=\frac{({{m}_{2}}gl\cos {{30}^{o}})-N(2\sin {{30}^{o}})}{({{m}_{2}}){{(2l)}^{2}}/3}\] \[\frac{(\sqrt{3}mgl/2)-\frac{32m{{l}^{2}}\alpha }{3\sqrt{3}}}{(4m{{l}^{2}}/3)}\] \[=\left( \frac{3\sqrt{3}g}{8l}-\frac{8}{\sqrt{3}}\alpha  \right)\]


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