9th Class Science Gravitation and Floatation Question Bank Gravitation

  • question_answer
    Average distance of the earth from the sun is\[{{L}_{1}}\]. If one year of the earth = D days, one year of another planet whose average distance from the sun is \[{{L}_{2}}\] will be

    A) \[D{{\left( \frac{{{L}_{2}}}{{{L}_{1}}} \right)}^{1/2}}days\]  

    B) \[D{{\left( \frac{{{L}_{2}}}{{{L}_{1}}} \right)}^{3/2}}days\]  

    C) \[D{{\left( \frac{{{L}_{2}}}{{{L}_{1}}} \right)}^{2/3}}days\]  

    D) \[D\left( \frac{{{L}_{2}}}{{{L}_{1}}} \right)days\]

    Correct Answer: B

    Solution :

    According to Kepler's third law, \[{{T}^{2}}\propto {{r}^{3}}\] or \[T\propto {{r}^{3/7}}\] \[\therefore \frac{D'}{D}={{\left( \frac{{{L}_{2}}}{{{L}_{1}}} \right)}^{3/2}}\] or \[D'=D{{\left( \frac{{{L}_{2}}}{{{L}_{1}}} \right)}^{3/2}}days\]


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