2. Solved Papers
  3. Manipal Engineering

Manipal Engineering Manipal Engineering Solved Paper-2013

  • question_answer
    If the scalar projection of the vector\[x\mathbf{i}-\mathbf{j}+\mathbf{k}\]on the vector\[2\mathbf{i}-\mathbf{j}+5\mathbf{k}\]is\[\frac{1}{\sqrt{30}}\]then value of re is equal to

    A) \[\frac{-5}{2}\]                                 

    B) \[6\]

    C) \[-6\]                    

    D)        \[3\]

    Correct Answer: A

    Solution :

    Projection of\[x\mathbf{i}-\mathbf{j}+\mathbf{k}\]on\[2\mathbf{i}-\mathbf{j}+5\mathbf{k}\] \[=\frac{(x\mathbf{i}-\mathbf{j}+\mathbf{k})\cdot (2\mathbf{i}-\mathbf{j}+5\mathbf{k})}{\sqrt{4+1+25}}=\frac{2x+1+5}{\sqrt{30}}\] But, given\[\frac{2x+6}{\sqrt{30}}=\frac{1}{\sqrt{30}}\] \[\Rightarrow \]               \[2x+6=1\] \[\Rightarrow \]               \[x=\frac{-5}{2}\]


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