RAJASTHAN PMT Rajasthan - PMT Solved Paper-2009

  • question_answer
    If two spheres of same masses and radius are brought in contact, then the force of attraction between them will be proportional to

    A)  \[{{r}^{2}}\]                                      

    B)  \[{{r}^{3}}\]

    C)  \[{{r}^{6}}\]                      

    D)         \[{{r}^{4}}\]

    Correct Answer: D

    Solution :

    Gravitational force acting between the spheres,                 \[F=G\frac{m\cdot m}{{{(2r)}^{2}}}\]                 \[=\frac{G\cdot \frac{4}{3}\pi {{r}^{3}}\times {{\rho }_{1}}\times \frac{4}{3}\times \pi {{r}^{3}}\times {{\rho }_{2}}}{4{{r}^{2}}}\]                 \[=\frac{4}{9}G{{\pi }^{2}}{{\rho }_{1}}{{\rho }_{2}}{{r}^{4}}\] \[\therefore \]  \[F\propto {{r}^{4}}\]


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