JEE Main & Advanced Physics Two Dimensional Motion Question Bank Critical Thinking

  • question_answer
    The driver of a car travelling at velocity v suddenly see a broad wall in front of him at a distance d. He should             [IIT 1977]

    A)             Brake sharply

    B)               Turn sharply

    C)             (a) and (b) both          

    D)             None of the above

    Correct Answer: A

    Solution :

                    When driver applies brakes and the car covers distance x before coming to rest, under the effect of retarding force F then \[\frac{1}{2}m{{v}^{2}}=Fx\]Þ \[x=\frac{m{{v}^{2}}}{2F}\] But when he takes turn then \[\frac{m{{v}^{2}}}{r}=F\]Þ \[r=\frac{m{{v}^{2}}}{F}\] It is clear that \[x=r/2\] i.e. by the same retarding force the car can be stopped in a less distance if the driver apply breaks. This retarding force is actually a friction force.


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