9th Class Science Time and Motion Question Bank Motion

  • question_answer
    A motor car is travelling 30 m/s on a circular road of radius 500 m. It is increasing in speed at the  rate of 2\[\text{m}/{{\text{s}}^{\text{2}}}\]. What is its acceleration?

    A)  \[\text{3}.0\text{ m}/{{\text{s}}^{\text{2}}}\]

    B)  \[\text{2}.\text{7 m}/{{\text{s}}^{\text{2}}}\]  

    C)  \[\text{1}.\text{8 m}/{{\text{s}}^{\text{2}}}\]

    D)  \[\text{2}.\text{5 m}/{{\text{s}}^{\text{2}}}\]

    Correct Answer: B

    Solution :

     Radial acceleration due to circular path,             \[{{a}_{r}}=\frac{{{v}^{2}}}{r}=\frac{{{(30)}^{2}}}{500}=\frac{9}{5}=1.8\,\,m/{{s}^{2}}\] Tangential acceleration due to increase in tangential speed             \[{{a}_{t}}=\frac{\Delta v}{\Delta t}=2\,\,m/{{s}^{2}}\] \[\therefore \]Net acceleration, \[{{a}_{t}}=\sqrt{{{a}_{r}}^{2}+{{a}_{t}}^{2}}\]             \[=\sqrt{{{(1.8)}^{2}}+{{(2)}^{2}}}\]             \[=\mathbf{2}\mathbf{.7}\,\,\mathbf{m/}{{\mathbf{s}}^{\mathbf{2}}}\]


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