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JEE Main & Advanced JEE Main Paper (Held on 10-4-2019 Afternoon)

  • question_answer
    A bullet of mass 20 g has an initial speed of \[1m{{s}^{-1}},\] just before it starts penetrating a mud wall of thickness 20 cm. if the wall offers a mean resistance of \[2.5\times {{10}^{2}}N,\] the speed of the bullet after emerging from the other side of the wall is close to:                             [JEE Main 10-4-2019 Afternoon]

    A) \[0.4m{{s}^{-1}}\]

    B)               \[0.1m{{s}^{-1}}\]

    C) \[0.3m{{s}^{-1}}\]              

    D) \[0.7m{{s}^{-1}}\]

    Correct Answer: D

    Solution :

    \[m=20\text{ }g,u=1\text{ }m/s,\text{v}=?\] \[S=20\times {{10}^{-2}}m\]                      \[a=\frac{-2.5\times {{10}^{-2}}}{20\times {{10}^{-3}}}m/{{s}^{2}}\] \[{{\text{v}}^{2}}={{u}^{2}}+2as\] \[{{\text{v}}^{2}}=1-2\times \frac{2.5\times {{10}^{-2}}}{20\times {{10}^{-3}}}\times \frac{20}{100}\] \[\text{v=}\frac{1}{\sqrt{2}}\simeq 0.7m/s\]


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