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

  • question_answer
    Acceleration due to gravity on the surface of moon is\[\text{1}/{{\text{5}}^{th}}\]that at the surface of the earth. If radius of the moon is\[\text{1}/{{4}^{th}}\]that of the earth, ratio of the mass of the earth to mass of moon is

    A)  20                         

    B)  40    

    C)  60                         

    D)  80

    Correct Answer: D

    Solution :

       On the earth\[g=\frac{GM}{{{R}^{2}}}\Rightarrow M=\frac{g{{R}^{2}}}{G}\] On the moon\[\frac{g}{5}=\frac{GM'}{{{(R/4)}^{2}}}\Rightarrow M'=\frac{g{{R}^{2}}}{80G}=\frac{M}{80}\]


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