JCECE Engineering JCECE Engineering Solved Paper-2006

  • question_answer
    If percentage decrease in radius of earth is \[1%\] without changing its mass, then percentage change in acceleration due to gravity is:

    A)  \[2%\] decrease             

    B)  \[2%\] increase

    C)   \[1%\] decrease            

    D)   \[1%\] increase

    Correct Answer: B

    Solution :

    The acceleration due to gravity g is given by                 \[g=\frac{GM}{{{R}^{2}}}\]                                          ? (i) where \[G\] is gravitational constant, \[M\] the mass, \[R\] the radius of earth. Taking \[\log \] on both sides, we get                 \[\log g=\log G+\log M-2\log R\] Differentiating, we get                 \[\frac{\Delta g}{g}=0+0-\frac{2\Delta R}{R}\] Given,   \[\frac{\Delta R}{R}=-1%\] \[\therefore \]  \[\frac{\Delta g}{g}=-2(-1%)=2%\]increase


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