BCECE Medical BCECE Medical Solved Papers-2015

  • question_answer
    Two trains A and B of length 400 m each are moving on two parallel tracks with a uniform speed of 72 \[km{{h}^{-1}}\]m the same direction, with A head of speed B. The driver of B decides to overtake A and accelerates by \[1\,m/{{s}^{-2}}\]. If after 50 s, the guard of B just brushes past the driver of A, what was the original distance between them?

    A)  100 m  

    B)  1150 m

    C)  1300 m

    D)  1250 m

    Correct Answer: D

    Solution :

    Given that, \[{{u}_{A}}={{u}_{B}}=72\,km{{h}^{-1}}=72\times \frac{5}{18}=20\,\,m{{s}^{-1}}\] Using the relations, \[s=ut+\frac{1}{2}a{{t}^{2}}\], we get       \[{{s}_{B}}={{u}_{B}}t+\frac{1}{2}a{{t}^{2}}=20\times 50+\frac{1}{2}\times 1\times {{(50)}^{2}}\]       \[{{s}_{B}}=100+1250=2250\,\,m\] Also, let \[{{s}_{A}}\] be the distance covered by the train A, then \[{{s}_{A}}={{u}_{A}}\times t\]                 \[=20\times 50=1000\,m\] Original distance between the two trains                 \[={{s}_{B}}-{{s}_{A}}\] \[=2250-1000=1250\,\,m\]


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