JEE Main & Advanced JEE Main Paper (Held On 09-Jan-2019 Evening)

  • question_answer
    In a car race on straight road, car A takes a time t less than car B at the finish and passes finishing point with a speed 'v' more than that of car B. Both the cars start, from rest and travel with constant acceleration \[{{a}_{1}}\text{ }and\text{ }{{a}_{2}}\] respectively. Then 'v' is equal to: [JEE Main Online Paper (Held On 09-Jan-2019 Evening]

    A) \[\sqrt{{{a}_{1}}\,{{a}_{2}}}\,\,t\] 

    B) \[\frac{2{{a}_{1}}{{a}_{2}}}{{{a}_{1}}+{{a}_{2}}}\,\,t\]

    C) \[\frac{{{a}_{1}}+{{a}_{2}}}{2}\,\,t\]     

    D) \[\sqrt{2{{a}_{1}}{{a}_{2}}}\,\,t\]

    Correct Answer: A

    Solution :

    \[S=\frac{1}{2}{{a}_{1}}{{t}^{2}}=\frac{1}{2}{{a}_{2}}{{({{t}_{0}}+t)}^{2}}\] \[V\,\,=\,\,(\sqrt{{{a}_{1}}}-\sqrt{{{a}_{2}}})\,\,\times \,\,\sqrt{2s}\] \[\left( \frac{1}{\sqrt{{{a}_{2}}}}-\frac{1}{\sqrt{{{a}_{2}}}} \right)\,\,\times \,\sqrt{2S}\,=\,\,t\] \[\sqrt{2S}\,=\,\frac{\sqrt{{{a}_{1}}}\sqrt{{{a}_{2}}t}}{\sqrt{{{a}_{1}}}\,-\,\sqrt{{{a}_{2}}}}\] \[V\,\,=\,\,\sqrt{{{a}_{1}}{{a}_{2}}t}\]                 


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