RAJASTHAN PMT Rajasthan - PMT Solved Paper-2005

  • question_answer
    The velocity of bullet is reduced from 200 m/s    to 100 m/s while travelling through a wooden block of thickness of 10 cm. The retardation assuming to be uniform, will be:

    A)  \[15\times {{10}^{4}}m/{{s}^{2}}\]

    B)         \[13.5\times {{10}^{4}}m/{{s}^{2}}\]

    C)  \[12\times {{10}^{4}}m/{{s}^{2}}\]

    D)         none of these

    Correct Answer: A

    Solution :

    Here: Initial velocity = 200 m/s Final velocity \[(\upsilon )\] = 100 m/s distance s = 10 cm = 0.1 m Using the relation of equation of motion \[{{\upsilon }^{2}}={{u}^{2}}+2as\] \[a=\frac{{{\upsilon }^{2}}-{{u}^{2}}}{2s}=\frac{{{(100)}^{2}}-{{(200)}^{2}}}{2\times 0.1}\] \[=\frac{10000-40000}{2\times 0.1}=\frac{-30000}{2}\] \[\begin{align}   & =-150000\,m/{{s}^{2}} \\  & =-15\times {{10}^{4}}\,m/{{s}^{2}} \\ \end{align}\] (-) minus sign denotes retardation


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