2. Questions Bank
  3. 9th Class
  4. Science
  5. Gravitation and Floatation

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

  • question_answer
    A sphere of mass 40 kg is attrached by another of mass 15 kg when their centres are 0.2 mapart, with a force of\[\text{9}.\text{8}\times \text{l}{{0}^{-\text{7}}}\text{ N}\text{.}\] Calculate the constant of gravitation.

    A)  \[9.2\times {{10}^{-7}}N{{m}^{2}}k{{g}^{-2}}\]

    B)  \[6.13\times {{10}^{-11}}N{{m}^{2}}k{{g}^{-2}}\]

    C)  \[6.53\times {{10}^{-18}}N{{m}^{2}}k{{g}^{-2}}\]

    D)  \[6.53\times {{10}^{-11}}N{{m}^{2}}k{{g}^{-2}}\]

    Correct Answer: D

    Solution :

       We know that, \[F=G\frac{{{m}_{1}}{{m}_{2}}}{{{r}^{2}}}\,or\,\,G=\frac{F{{r}^{2}}}{{{m}_{1}}{{m}_{2}}}\] Given, \[F=9.8\times {{10}^{-7}}N,\,\,r=0.2\,\,m,\] \[{{m}_{1}}=40kg,\,\,{{m}_{2}}=15\,kg\] \[\therefore \,\,G=\frac{9.8\times {{10}^{-7}}\times {{(0.2)}^{2}}}{40\times 15}=6.53\times {{10}^{-11}}N{{m}^{2}}k{{g}^{-2}}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner