Let $\overrightarrow a = \widehat i + \widehat j - \widehat k$ and $\overrightarrow c = 2\widehat i - 3\widehat j + 2\widehat k$. Then the number of vectors $\overrightarrow b$ such that $\overrightarrow b \times \overrightarrow c = \overrightarrow a$ and $|\overrightarrow b | \in$ {1, 2, ........, 10} is :
Solution
<p>$\overrightarrow a = \widehat i + \widehat j - \widehat k$</p>
<p>$\overrightarrow c = 2\widehat i - 3\widehat j + 2\widehat k$</p>
<p>Now, $\overrightarrow b \times \overrightarrow c = \overrightarrow a$</p>
<p>$$\overrightarrow c \,.\,(\overrightarrow b \times \overrightarrow c ) = \overrightarrow c \,.\,\overrightarrow a $$</p>
<p>$\overrightarrow c \,.\,\overrightarrow a = 0$</p>
<p>$$ \Rightarrow (\widehat i + \widehat j - \widehat k)(2\widehat i - 3\widehat j + 2\widehat k) = 0$$</p>
<p>$= 2 - 3 - 2 = 0$</p>
<p>$\Rightarrow - 3 = 0$ (Not possible)</p>
<p>$\Rightarrow$ No possible value of $\overrightarrow b$ is possible.</p>
About this question
Subject: Mathematics · Chapter: Vector Algebra · Topic: Types of Vectors
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