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9th Class Science Time and Motion Question Bank Motion

  • question_answer
    While testing the safety of a car, a dummy driver is used and the car is propelled at different speeds to hit a rigid wall. In one such test, the dummy driver had a mass of \[70\,\,kg\] and the speed of the car just before the impact was\[40\,\,m\,\,{{s}^{-1}}\]. If the time interval between the collision and the car coming to rest was\[0.2\,\,s\], then find the deceleration of the car due to impact.

    A) \[200\,\,m\,\,{{s}^{-2}}\]           

    B)        \[80\,\,m\,\,{{s}^{-2}}\]

    C) \[110\,\,m\,\,{{s}^{-2}}\]         

    D)        \[280\,\,m\,\,{{s}^{-2}}\]

    Correct Answer: A

    Solution :

     Initial velocity of the car \[=40\,\,m\,\,{{s}^{-1}}\], Final velocity of the car\[=0\], Time\['t'=0.2\,\,s\]             \[a=\frac{v-u}{t}=\frac{0-40}{0.2}=-200\,\,m\,\,{{s}^{-2}}\] \[\therefore \]Deceleration\[=200\,\,m\,\,{{s}^{-2}}\]


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