2. Solved Papers
  3. JCECE Engineering

JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    If the force represented by \[\mathbf{i}+\mathbf{j}+\mathbf{k}\] is acting through the point \[5\mathbf{i}+4\mathbf{j}-3\mathbf{k}\], then its moment about the point\[(1,\,\,2,\,\,2)\]is

    A) \[14\mathbf{i}-8\mathbf{j}+12\mathbf{k}\]

    B) \[-14\mathbf{i}-8\mathbf{j}-12\mathbf{k}\]

    C) \[7\mathbf{i}+9\mathbf{j}+2\mathbf{k}\]

    D) \[7\mathbf{i}-9\mathbf{j}+2\mathbf{k}\]

    Correct Answer: D

    Solution :

    We have,                 \[\mathbf{F}=\mathbf{i}+\mathbf{j}+\mathbf{k}\] Let\[P(5,\,\,4,\,\,-3)\]and\[O(1,\,\,2,\,\,2)\]be given points. Then,    \[OP=4\mathbf{i}+2\mathbf{j}-5\mathbf{k}\] Now, moment of \[\mathbf{F}\] about \[O\]                 \[=r\times F\left| \begin{matrix}    \mathbf{i} & \mathbf{j} & \mathbf{k}  \\    4 & 2 & -5  \\    1 & 1 & 1  \\ \end{matrix} \right|\]                 \[=(2+5)\mathbf{i}-(4+5)\mathbf{j}+(4-2)\mathbf{k}\]


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