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JEE Main & Advanced Sample Paper JEE Main Sample Paper-25

  • question_answer
    A bullet of mass 10 g is fired horizontally with a velocity \[1000\,m{{s}^{-1}}\] from a rifle situated at a height 50 m above the ground. If the bullet reaches the ground with a velocity \[500\,m{{s}^{-1}}\], the work done against air resistance in the trajectory of the bullet is (take \[g=10\,m{{s}^{-2}}\])

    A)  5005 J                         

    B)  3755 J

    C)  3750 J                         

    D)  \[17.5\] J

    Correct Answer: C

    Solution :

    From equation of motion, \[{{v}^{2}}=\text{ }{{u}^{2}}-\]2as \[{{\left( 500 \right)}^{2}}={{\left( 1000 \right)}^{2}}-2\times a\times s\] \[s=\frac{{{(1000)}^{2}}-{{(500)}^{2}}}{2a}=\frac{375000}{a}\] \[\therefore \]  Work done against air resistance, \[W=Fs=ma\,\,\times s\] \[=\frac{10}{1000}a\times \frac{375000}{a}=\,3750\,J\]


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