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9th Class Science Force and laws of motion Question Bank Force and Laws of Motion

  • question_answer
    A bullet fired into a wall loses half of its velocity after penetrating 3 cm. Further it can penetrate a maximum of

    A)  3 cm                                     

    B)  2 cm

    C)  1cm                        

    D)         0.5cm

    Correct Answer: C

    Solution :

     Remaining velocity after penetrating \[3\,\,cm\] is half. So, remaining kinetic energy is one-fourth. So, the kinetic energy lost is three-fourth. In penetrating further, it will lose an additional energy of one-fourth. Applying work-energy theorem,             \[\frac{3}{4}KE=F\times s\] and       \[\frac{1}{4}KE=F\times s'\] \[\therefore \]            \[s=\frac{s'}{3}\]


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