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JEE Main & Advanced Physics NLM, Friction, Circular Motion Question Bank Second Law of Motion

  • question_answer
    A body of mass 5 kg starts from the origin with an initial velocity \[\overrightarrow{u\,}\,=\,30\hat{i}+40\hat{j}\,m{{s}^{-1}}\]. If a constant force \[\overrightarrow{F\,}=-(\hat{i}+5\hat{j})N\] acts on the body, the time in which the y?component of the velocity becomes zero is [EAMCET (Med.) 2000]

    A)             5 seconds

    B)               20 seconds

    C)             40 seconds

    D)               80 seconds

    Correct Answer: C

    Solution :

                    \[{{u}_{y}}=40\,m/s\], \[{{F}_{y}}=-5N\], \[m=5\,kg\]. So \[{{a}_{y}}=\frac{{{F}_{y}}}{m}=-1\,m/{{s}^{2}}\] (As \[v=u+at\]) \ \[{{v}_{y}}=40-1\times t=0\] Þ \[t=40\,\sec \].


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