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9th Class Science Gravitation and Floatation Question Bank Gravitation Conceptive Objective Problems

  • question_answer
    A sphere of mass 40 kg is attracted by a second sphere of mass 60 kg with a force equal to\[4\times {{10}^{-5}}N\].If\[G=6\times {{10}^{-11}}N{{m}^{2}}/k{{g}^{2}},\] calculate the distance between the two spheres.

    A)  3 cm.                   

    B)  6 cm.

    C)  9 cm.                   

    D)  10 cm.

    Correct Answer: B

    Solution :

       Here, \[{{m}_{1}}=40kg,\,\,{{m}_{2}}=60kg,\] \[F=4\times {{10}^{-5}}N,\,\,G=6\times {{10}^{-11}}N{{m}^{2}}/k{{g}^{2}}.\] As \[F=G\frac{{{m}_{1}}{{m}_{2}}}{{{r}^{2}}}\] \[r=\sqrt{\frac{G{{m}_{1}}{{m}_{2}}}{F}}\] \[=\sqrt{\frac{6\times {{10}^{-11}}\times 40\times 60}{4\times {{10}^{-5}}}}\] \[=\sqrt{36\times {{10}^{-4}}}=6\times {{10}^{-2}}m\] \[=6\times {{10}^{-2}}\times 100\,cm=6cm.\]


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