MCQ
The projection of vector $\hat{i}$ on the vector $\hat{i}+\hat{j}+2 \hat{k}$ is:
  • A
    $\frac{1}{\sqrt{6}}$
  • B
    $\sqrt{6}$
  • C
    $\frac{2}{\sqrt{6}}$
  • D
    $\frac{3}{\sqrt{6}}$

Answer

Let, $\vec{a}=\hat{i}$ and $\vec{b}=\hat{i}+\hat{j}+2 \hat{k}$
We know that, projection of vector $\vec{a}$ on $\vec{b}=\frac{\vec{a} \cdot \vec{b}}{|\vec{b}|}$
$
=\frac{\hat{i} \cdot(\hat{i}+\hat{j}+2 \hat{k})}{\sqrt{1^2+1^2+2^2}}=\frac{1}{\sqrt{6}}$

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