JEE Main & Advanced Sample Paper JEE Main Sample Paper-43

  • question_answer
    Let\[(0,\,1)\to \,(0,1)\]be a differential function such that \[f'(x)\ne 0\] for all \[x\,\in (0,\,\,1)\]and \[f\,\left( \frac{1}{2} \right)=\frac{\sqrt{3}}{2}\]. Suppose for all \[x\],
    \[\underset{t\to x}{\mathop{\lim }}\,\,\frac{\int\limits_{0}^{t}{\sqrt{1-{{\{f(S)\}}^{2}}}\,dS-\int\limits_{0}^{x}{\sqrt{1-{{\{f(S)\}}^{2}}}dx}}}{f(t)-f(x)}\]
    Then, the value of \[f\left( \frac{1}{4} \right)\] belongs to

    A)  \[\left\{ \sqrt{7},\,\,\sqrt{15} \right\}\]            

    B)  \[\left\{ \frac{\sqrt{7}}{2},\,\,\frac{\sqrt{15}}{2} \right\}\]

    C)  \[\left\{ \frac{\sqrt{7}}{3},\,\,\frac{\sqrt{15}}{3} \right\}\]              

    D)  \[\left\{ \frac{\sqrt{7}}{4},\,\,\frac{\sqrt{15}}{4} \right\}\]

    Correct Answer: D

    Solution :

     Given \[\Rightarrow \] \[v'\frac{v}{\sqrt{2}}\] for all \[E=\frac{1}{2}mv{{'}^{2}}+\frac{1}{2}mv{{'}^{2}}+\frac{1}{2}(2m){{v}^{2}}\] \[=mv{{'}^{2}}+m{{v}^{2}}\] \[\Rightarrow \] By L ?Hospital rule, \[m{{\left( \frac{v}{\sqrt{2}} \right)}^{2}}+m{{v}^{2}}=\frac{3}{2}m{{v}^{2}}\] \[{{T}_{1}}-{{T}_{2}}=12a\]         \[{{T}_{2}}=3a\] \[{{T}_{2}}\] \[Eq\]               \[{{T}_{1}}=15a\] \[\therefore \]    \[\frac{{{T}_{1}}}{{{T}_{2}}}=\frac{15a}{3a}=\frac{5}{1}\] \[\Rightarrow \]            \[{{T}_{1}}:{{T}_{2}}=5:1\] \[T=M\,\left( g-\frac{g}{4} \right)=\frac{3Mg}{4}\]  \[W=\mathbf{T}\cdot \mathbf{d}\Rightarrow \,W=Td\] \[\Rightarrow \]            \[W=-Td=-\frac{3Mgd}{4}\] \[\Sigma mvr=\,({{l}_{system}})\omega \]    \[\Rightarrow \] \[mv\frac{l}{2}=\frac{(2m)\,{{(2l)}^{2}}}{12}\omega =\frac{2m(4{{l}^{2}})}{12}\omega \]            \[\Rightarrow \]


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