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JCECE Medical JCECE Medical Solved Paper-2002

  • question_answer
    A particle moves along a straight line such that its displacement at any time t is given by \[s={{t}^{3}}-3{{t}^{2}}+2m.\]The displacement when the acceleration bec6mes zero is:

    A)  zero           

    B)  2 m

    C)  3m            

    D)  -2m

    Correct Answer: A

    Solution :

     Key Idea: Acceleration is equal to rate of change of velocity. Given, \[s={{t}^{3}}-3{{t}^{2}}+2\] Velocity    \[v=\frac{ds}{dt}=3{{t}^{2}}-6t\] Acceleration \[a=\frac{{{d}^{2}}s}{d{{t}^{2}}}=\frac{dv}{dt}=6t-6\] At \[a=0,\]we have \[6t-6=0\]              \[\Rightarrow \] \[t=1\,s\]              Hence, \[s={{(1)}^{3}}-3{{(1)}^{2}}+2\] \[=1-3+2=0\]


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