Aspire Faculty ID #11963 · Topic: NIMCET 2025 · Just now
NIMCET 2025

If $\vec{a}=\hat{i}+\hat{j}+\hat{k}$, $\vec{b}=2\hat{i}-\hat{j}+3\hat{k}$ and $\vec{c}=\hat{i}-2\hat{j}+\hat{k}$, then a vector of magnitude $\sqrt{22}$ which is parallel to $2\vec{a}-\vec{b}+3\vec{c}$ is

Solution

Given: $\vec{a} = \hat{i} + \hat{j} + \hat{k}$ 
$\vec{b} = 2\hat{i} - \hat{j} + 3\hat{k}$ 
$\vec{c} = \hat{i} - 2\hat{j} + \hat{k}$ 

Compute: $2\vec{a} - \vec{b} + 3\vec{c}$ 

First: 
$2\vec{a} = 2\hat{i} + 2\hat{j} + 2\hat{k}$ 
$-\vec{b} = -2\hat{i} + \hat{j} - 3\hat{k}$ 
$3\vec{c} = 3\hat{i} - 6\hat{j} + 3\hat{k}$ 

Add components: 
$i$–component: $2 - 2 + 3 = 3$ 
$j$–component: $2 + 1 - 6 = -3$ 
$k$–component: $2 - 3 + 3 = 2$ 
So the vector: $\vec{v} = 3\hat{i} - 3\hat{j} + 2\hat{k}$ 
Its magnitude: $|\vec{v}| = \sqrt{3^2 + (-3)^2 + 2^2} = \sqrt{9 + 9 + 4} = \sqrt{22}$ 
We need a vector parallel to $\vec{v}$ with magnitude $\sqrt{22}$. 
Since $|\vec{v}| = \sqrt{22}$, the required vector is simply: $\boxed{3\hat{i} - 3\hat{j} + 2\hat{k}}$

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