JEE Main & Advanced Sample Paper JEE Main - Mock Test - 20

  • question_answer
    A student measures the distance traversed in free fall of a body, initially at rest, in a given time. He uses this data to estimate g, the acceleration due to gravity. If the maximum percentage errors in measurement of the distance and the time are \[{{e}_{1}}\] and \[{{e}_{2}}\]respectively, the percentage error in the estimation of g is

    A) \[{{e}_{2}}-{{e}_{1}}\]           

    B) \[{{e}_{1}}+2{{e}_{2}}\]

    C) \[{{e}_{1}}+{{e}_{2}}\]         

    D) \[{{e}_{1}}-2{{e}_{2}}\]

    Correct Answer: B

    Solution :

    [b]: From the relation, \[h=ut+\frac{1}{2}g{{t}^{2}}\]\[h=\frac{1}{2}g{{t}^{2}}\]\[\Rightarrow \]\[g=\frac{2h}{{{t}^{2}}}\](\[\because \]\[u=0,\]body initially at rest) Taking natural logarithm on both sides, we get In g = In h - 2 In t Differentiating, \[\frac{\Delta g}{g}=\frac{\Delta h}{h}-2\frac{\Delta t}{t}\] For maximum permissible error, or\[{{\left( \frac{\Delta g}{g}\times 100 \right)}_{\max }}=\left( \frac{\Delta h}{h}\times 100 \right)+2\times \left( \frac{\Delta t}{t}\times 100 \right)\] According to problem \[\frac{\Delta g}{h}\times 100={{e}_{1}}\]and\[\frac{\Delta t}{t}\times 100={{e}_{2}}\] Therefore, \[{{\left( \frac{\Delta t}{g}\times 100 \right)}_{\max }}={{e}_{1}}+2{{e}_{2}}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner