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NEET Sample Paper NEET Sample Test Paper-6

  • question_answer
    A body of mass 1kg is thrown upward with a velocity of \[10m/s\] comes to rest (momentarily) after moving up to 4km. The work done by air drag in this process is (Take, \[g=10m/{{s}^{2}}\])

    A)  \[-20J\]                       

    B)  \[-10J\]

    C)  \[-30J\]                       

    D)  \[0J\]

    Correct Answer: B

    Solution :

    According to work energy theorem \[{{w}_{gravitational\text{ }force}}+{{w}_{air\,drag}}=\] change in KE \[\Rightarrow \]  \[mg.\Delta r+{{w}_{air\,drag}}=\] change in KE \[\Rightarrow \] \[-mgh+{{w}_{air\,drag}}\] change in KE \[\Rightarrow \]  \[{{w}_{air\,\,drag}}=\] change in KE + mgh             \[=\left[ 0-\frac{1}{2}m{{u}^{2}} \right]+mgh\]                 \[=-50J+40J=-10J\]


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