KVPY Sample Paper KVPY Stream-SX Model Paper-17

  • 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 from rest from rest and travel with constant acceleration \[a{{ }_{1}}\] and \[a{{ }_{2}}\] respectively. Then 'v' is equal to:

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

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

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

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

    Correct Answer: C

    Solution :

    \[\sqrt{\frac{2\ell }{{{a}_{2}}}}-\sqrt{\frac{2\ell }{{{a}_{1}}}}=t\]
    \[\Rightarrow \]\[\frac{\sqrt{2\ell }}{t}=\frac{\sqrt{{{a}_{1}}{{a}_{2}}}}{\sqrt{{{a}_{1}}}-\sqrt{{{a}_{2}}}}\]
    \[\sqrt{2{{a}_{1}}\ell }-\sqrt{2{{a}_{2}}\ell }=v\]
    \[\Rightarrow \] \[\frac{\sqrt{2\ell }}{v}=\frac{1}{\sqrt{a{{ & }_{1}}}-\sqrt{{{a}_{2}}}}\]\[\Rightarrow \]\[\frac{v}{t}=\sqrt{{{a}_{1}}{{a}_{2}}}\]\[\Rightarrow \]\[v=\left( \sqrt{{{a}_{1}}{{a}_{2}}} \right)t.\]


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