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JEE Main & Advanced Sample Paper JEE Main Sample Paper-23

  • question_answer
    A body of mass 5 kg starts from the origin with an initial velocity \[u=(30\,\hat{i}+40\hat{j})m{{s}^{-1}}\] If a constant force \[(-6\hat{i}+5\hat{j})N\] acts on the body, the time in which the y component of the velocity becomes zero is:

    A)  5 s                              

    B)  20 s

    C)  40 s                            

    D)  80 s

    Correct Answer: C

    Solution :

    From Newton?s second law of motion. Force = mass\[\times \] acceleration \[{{a}_{y}}=-\frac{5}{5}\,m{{s}^{-2}}\,=-1\,m{{s}^{-2}}\] From equation of motion \[{{v}_{y}}={{u}_{y}}+{{a}_{y}}t\] Where   \[{{v}_{y}}\] is initial velocity along y-axis, t is the time and \[{{v}_{y}}\] is the final velocity along y-axis. Given \[{{v}_{y}}=0,\,\,{{u}_{y}}=40\,\,m{{s}^{-1}},\,\,{{a}_{y}}=-1\,\,m{{s}^{-1}}\] \[\therefore \,\,\,\,\,\,\,\,0=40-1\times t\]\[\Rightarrow \,\,t=40\,s\]


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