9th Class Science Time and Motion Question Bank MCQs - Motion

  • question_answer
    A woman is wearing her seat belt, while driving at 60 km/h. She finds it necessary to slam on her brakes and slows uniformly to a stop in 1.6 s. What is the average acceleration experienced by her?

    A) \[-10.4\ m/{{s}^{2}}\]         

    B) \[10.4\ m/{{s}^{2}}\]

    C) \[1.04\ m/{{s}^{2}}\]         

    D) \[-1.04\ m/{{s}^{2}}\]

    Correct Answer: A

    Solution :

    [a] Given, u = 60 km/h = \[60\frac{5}{18}\operatorname{m}/s=\frac{50}{3}\operatorname{m}/s,\]
              \[t=1.6\ s,v=0\]
    \[\therefore \] Average acceleration,
    \[a=\frac{v-u}{t}=\frac{0-\frac{50}{3}}{1.6}=\frac{-50}{3\times 1.6}\]
    \[=\frac{-100}{3\times 3.2}=\frac{-1000}{96}\]
    \[=-10.4\operatorname{m}/{{s}^{2}}\]
     


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