JEE Main & Advanced Mathematics Vector Algebra Question Bank Application of vectors in three dimensional geometry

  • question_answer
    The position vector of the point where the line \[\mathbf{r}=\mathbf{i}-\mathbf{j}+\mathbf{k}+t(\mathbf{i}+\mathbf{j}+\mathbf{k})\]meets the plane \[\mathbf{r}.(\mathbf{i}+\mathbf{j}+\mathbf{k})=5\]is [Kerala (Engg.) 2005]

    A)            \[5\mathbf{i}+\mathbf{j}-\mathbf{k}\]

    B)            \[5\mathbf{i}+3\mathbf{j}-3\mathbf{k}\]

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

    D)            \[5\mathbf{i}+\mathbf{j}+\mathbf{k}\]

    E)            \[4\mathbf{i}+2\mathbf{j}-2\mathbf{k}\]

    Correct Answer: B

    Solution :

               The point of the given line is \[(1+t,-1+t,1-t)\]                    Equation of plane is, \[x+y+z=5\]                    The point of the given line satisfies the equation of plane                    \[\therefore \]\[(1+t)(-1+t)+(1-t)=5\] Þ \[1+t=5\] Þ \[t=4\]                    \ Points are \[(5,\,\,3,\,-3)\]                    Hence, position vector of point is, \[5\mathbf{i}+3\mathbf{j}-3\mathbf{k}\].


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