CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2006

  • question_answer
    A physical quantity P is related to four measurable quantities a, b, c and d as follows \[P=\frac{{{a}^{3}}{{b}^{2}}}{\sqrt{c}d}\] The percentage errors of measurement in a, b, c and d are 1%, 3%, 4% and 2%. The percentage error in the quantity P is:

    A)  10%                      

    B)         13%

    C)  5%                        

    D)         15%

    E)  17%

    Correct Answer: B

    Solution :

    Given, \[P=\frac{{{a}^{3}}{{b}^{2}}}{\sqrt{c}d}={{a}^{3}}{{b}^{2}}{{c}^{-1/2}}{{d}^{-1}}\] The fractional error in P is given by \[\frac{\Delta P}{P}=3\frac{\Delta a}{a}+2\frac{\Delta b}{b}-\frac{1}{2}.\frac{\Delta c}{c}-\frac{\Delta d}{d}\] The maximum fractional error in P is \[\left( \frac{\Delta P}{P} \right)=3\frac{\Delta a}{a}+2\frac{\Delta b}{b}+\frac{1}{2}\frac{\Delta c}{c}+\frac{\Delta d}{d}\] The percentage error in P is \[{{\left( \frac{\Delta P}{P} \right)}_{\max }}\times 100=3\left( \frac{\Delta a}{a}\times 100 \right)\] \[+2\left( \frac{\Delta b}{b}\times 100 \right)+\frac{1}{2}\left( \frac{\Delta c}{c}\times 100 \right)+\frac{\Delta d}{d}\times 100\] = 3 (% error in a) + 2 (% error in b)      \[+\frac{1}{2}\](% error in c) + (% error in d) = 3 (1%) + 2 (3%)\[+\frac{1}{2}\](4%) + (2%) = 3% + 6% + 2% + 2% = 13%


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