JEE Main & Advanced JEE Main Paper (Held on 09-4-2019 Morning)

  • question_answer A solid sphere of mass 'M' and radius 'a' is surrounded by a uniform concentric spherical shell of thickness 2a and mass 2M. The gravitational field at distance '3a' from the centre will be: [JEE Main 9-4-2019 Morning]

    A) \[\frac{2GM}{9{{a}^{2}}}\]                      

    B) \[\frac{GM}{3{{a}^{2}}}\]

    C) \[\frac{GM}{9{{a}^{2}}}\]                        

    D) \[\frac{2GM}{3{{a}^{2}}}\]

    Correct Answer: B

    Solution :

    We use gauss's Law for gravitation \[g.4\pi {{r}^{2}}=\](Mass enclosed)\[4\pi G\] \[g=\frac{3M4\pi G}{4\pi {{(3a)}^{2}}}\]\[=\frac{MG}{3{{a}^{2}}}\] Option [b]

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