JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
    A physical quantity \[X\] is represented by\[X=[{{M}^{n}}{{L}^{-\theta }}{{T}^{-\phi }}]\]. The maximum percentage errors in the measurement of \[M,\,\,L\] and\[T\], respectively are \[\alpha %,\,\,\beta %\] and\[\gamma %\]. The maximum percentage error in the measurement of\[X\]will be

    A) \[(\eta \alpha -\theta \beta -\phi \gamma )%\]

    B) \[(\theta \beta +\phi \gamma -\eta \alpha )%\]

    C) \[\left( \frac{\alpha }{\eta }-\frac{\beta }{\theta }-\frac{\gamma }{\theta } \right)%\]    

    D)  \[(\eta \alpha +\theta \beta +\phi \gamma )%\]

    Correct Answer: D

    Solution :

    Given,\[X=[{{M}^{\eta }}{{L}^{-\theta }}{{T}^{-\phi }}]\] \[\therefore \]  \[\frac{\Delta X}{X}\times 100\] \[=\eta \left( \frac{\Delta M}{M}\times 100 \right)+\theta \left( \frac{\Delta L}{L}\times 100 \right)+\phi \left( \frac{\Delta T}{T}\times 100 \right)\]\[\Rightarrow \]      \[\frac{\Delta X}{X}\times 100=\eta (\alpha )+\theta (\beta )+\phi (\gamma )\] Thus, maximum percentage error in the measurement of \[X\] is given as                 \[\frac{\Delta X}{X}\times 100=(\eta \alpha +\theta \beta +\phi \gamma )%\]


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