BHU PMT BHU PMT (Mains) Solved Paper-2008

  • question_answer

    Directions : In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:

    The radius and mass of earth are increased by 0.5%.Which of the following are true at the surface of earth?  g will decrease  Escape velocity will remain unchanged  Potential energy will remain unchanged  g will increase

    A)  1, 2 and 3 are correct.

    B)  1 and 2 are correct.

    C)   2 and 4 are correct.

    D)  1 and 3 are correct.

    Correct Answer: A

    Solution :

                     \[g=\frac{GM}{{{R}^{2}}}\] \[{{v}_{e}}=\sqrt{\frac{2GM}{R}}\]and\[u=-\frac{G{{M}_{m}}}{R}\] \[\therefore \]\[g\propto \frac{M}{{{R}^{2}}},{{v}_{e}}\propto \sqrt{\frac{M}{R}}\]and\[U\propto \frac{M}{R}\] If both mass and radius are increased by 0.5% then Vg and £7 remains unchanged whereas g decrease by 0.5%.


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