2. Solved Papers
  3. WB JEE Medical

WB JEE Medical WB JEE Medical Solved Paper-2006

  • question_answer
    A passenger train is moving at \[5\,\text{m}{{\text{s}}^{-1}}.\] An express train is travelling at \[30\,\text{m}{{\text{s}}^{-1}},\] on the same track and rear side of the passenger tsrain at some distance. The driver in express train applied brakes to avoid collision. If the retardation due to brakes is \[4\,\text{m}{{\text{s}}^{-2}},\] the time in which the accident is avoided after the application of brakes is :

    A)  4.25 s                                   

    B)  5.25 s

    C)  6.25 s                                   

    D)  7.25 s

    Correct Answer: C

    Solution :

                     Initial relative velocity of the express trainw.r.t. the passenger train, \[{{u}_{ep}}={{u}_{e}}-{{u}_{p}}=30-5=25m{{s}^{-1}}\] Final relative velocity of the express train w.r.t.the passenger train, \[{{v}_{ep}}=0\] (because express train comes to rest) From first equation of motion \[{{v}_{ep}}={{u}_{ep}}-at\] or            \[0=25-4t\] or            \[4t=25\] or            \[t=6.25\,s\]


You need to login to perform this action.
You will be redirected in 3 sec spinner