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JEE Mains · Physics · STD 11 - Work,energy,power and collision
  • JEE Mains 2019
  • Medium
  • MCQ

A bullet of mass \(20\,g\) has an initial speed of \(1\,ms^{-1}\) just before it starts penetrating a mud wall of thickness \(20\,cm.\) If the wall offers a mean resistances of \(2.5 \times 10^{-2}\,N,\) the speed of the bullet after emerging from the other side of the wall is close to .............. \(\mathrm{ms}^{-1}\)

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Answer & Solution

Correct Answer

(A) \(0.7\)

Step-by-step Solution

Detailed explanation

\(\begin{array}{l}
2.5 \times {10^{ - 2}} \times 0.2 = \frac{1}{2} \times 20 \times {10^{ - 3}}\left\{ { - {V^2} + {1^2}} \right\}\\
5 \times {10^{ - 3}} = 10 \times {10^{ - 3}}\left( {1 - {V^2}} \right)\\
1 - {V^2} = \frac{1}{2}\,\,;\,\,{V^2} = \frac{1}{2}\,\,;\,\,V = \frac{1}{{\sqrt 2 }}\, = 0.7
\end{array}\)
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