9th Class Science Time and Motion Question Bank Motion IIT JEE Objective Problems

  • question_answer
    A car travelling at a speed of 30 kmph is brought to rest in 8m by applying brakes. If the same car is travelling at 60 kmph, it can be brought to a halt with the same braking force in a distance of:

    A)  8 m                       

    B)  16 m

    C)  24 m                    

    D)  32 m

    Correct Answer: D

    Solution :

    \[a=\frac{{{V}^{2}}-{{u}^{2}}}{2s}\]constant \[S\propto {{V}^{2}}={{u}^{2}}\frac{{{S}_{2}}}{{{S}_{1}}}=\frac{V_{2}^{2}-u_{2}^{2}}{{{v}^{2}}-{{u}^{2}}}\] \[(or)\,\,\frac{{{S}_{2}}}{8}=\frac{{{0}^{2}}-{{60}^{2}}}{{{0}^{2}}-{{30}^{2}}}\Rightarrow {{S}_{2}}=\frac{60\times 60\times 8}{30\times 30}=32m\]


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