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9th Class Science Time and Motion Question Bank Motion

  • question_answer
    Two paper screens A and B are separated by a distance of 100 m. A bullet pierces A and then B. The hole in B is 10 cm below the hole in A. If the bullet is travelling horizontally at A, calculate the velocity of the bullet at A. Neglect the resistance of paper in air.

    A)  100 m/sec

    B)  400 m/sec

    C)  550 m/sec

    D)  700 m/sec  

    Correct Answer: D

    Solution :

                \[t=\frac{R}{u}=\frac{100}{u}\]             \[h=\frac{1}{2}g{{t}^{2}}=\frac{9.8\times 100\times 100}{2{{u}^{2}}}\] \[\Rightarrow \]   \[{{u}^{2}}=\frac{9.8\times {{(100)}^{2}}}{2\times 0.1}=490000\] \[\Rightarrow \]   \[u=700\,\,m/\sec \]


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