Haryana PMT Haryana PMT Solved Paper-2006

  • question_answer
    A satellite is moving on a circular path of radius r around the earth has a time period T. If its radius slightly increases by \[\Delta r\], the change in its time period is :

    A)                 \[\frac{3}{2}\left( \frac{T}{r} \right)\Delta r\]                    

    B)  \[\left( \frac{T}{r} \right)\Delta r\]

    C)                  \[\frac{3}{2}\left( \frac{{{T}^{2}}}{{{r}^{2}}} \right)\Delta r\]                      

    D)  none of these 

    Correct Answer: A

    Solution :

                    According to Keplers law \[{{T}^{2}}=k{{r}^{3}}\] \[T=k{{r}^{3/2}}\] \[\frac{dT}{dr}=\frac{3}{2}\frac{k{{r}^{2}}}{T}\] \[\frac{dT}{dr}=\frac{3}{2}\left( \frac{T}{r} \right)\]                 \[\Rightarrow \]               \[\frac{\Delta T}{\Delta r}=\frac{3}{2}\left( \frac{T}{r} \right)\]                                 \[\Delta T=\frac{3}{2}\left( \frac{T}{r} \right)\Delta r\]


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