JCECE Engineering JCECE Engineering Solved Paper-2005

  • question_answer
    A particle moves along \[Y-\]axis in such a way that its \[y-\]coordinate varies with time \[t\] according to the relation \[y=3+5t+7{{t}^{2}}\]. The initial velocity and acceleration of the particle are respectively:

    A) \[14m{{s}^{-1}},\,\,5\,\,m{{s}^{-2}}\]

    B)  \[19m{{s}^{-1}},\,\,-9m{{s}^{-2}}\]

    C)  \[-14m{{s}^{-1}},\,\,-5m{{s}^{-2}}\]

    D)   \[5m{{s}^{-1}},\,\,14\,\,m{{s}^{-2}}\]

    Correct Answer: D

    Solution :

    Key Idea: Rate of change of position is known as velocity and rate of change of velocity is known as acceleration. Given                 \[y=3+5t+7{{t}^{2}}\] Velocity \[(v)\] is defined as rate of change of displacement, also using \[\frac{d}{dx}{{x}^{n}}=n{{x}^{n-1}},\]we have \[\therefore \]  \[v=\frac{dy}{dt}=5+14t\] Initial velocity at\[t=0\], is                                 \[v=5\,\,m/s\] Also acceleration\[a=\frac{{{d}^{2}}y}{d{{x}^{2}}}=14\,\,m/{{s}^{2}}\]


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