JEE Main & Advanced Sample Paper JEE Main Sample Paper-23

  • question_answer
    Weight of a body of mass m decreases by \[1%\] when it is raised to height h above the earth's surface. If the body is taken to a depth h in a mine, change in its weight is:

    A)  \[0.5%\] decrease          

    B)  \[2%\] decrease

    C)  \[0.5%\] increase           

    D)  \[1%\] increase

    Correct Answer: A

    Solution :

    At an altitude h, the acceleration due to gravity is \[g'=g\,\left( 1-\frac{2h}{{{R}_{e}}} \right)\Rightarrow \,mg'=mg\left( 1-\frac{2h}{{{R}_{e}}} \right)\]i.e., \[w'=w\,\left( 1-\frac{2h}{{{R}_{e}}} \right)\] \[\frac{99}{100}w=w\,\left( 1-\frac{2h}{{{R}_{e}}} \right)\,\Rightarrow \] i.e., \[h=0.005\,{{R}_{e}}\] At a point below, the surface of earth at depth h. The weights of body is given by                      \[w'=w\left( 1-\frac{h}{{{R}_{e}}} \right)\Rightarrow \,\frac{w'}{w}=0.995\]\[%\Delta w=\frac{(1-0.995)}{w}\times 100=0.5%\]


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