If vec A and vec B are perpendicular vectors and vector vec A = 5hat{i} + 7hat{j} - 3hat{k} and vec

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3-1.Vectors

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If $\vec A$ and $\vec B$ are perpendicular vectors and vector $\vec A = 5\hat i + 7\hat j - 3\hat k$ and $\vec B = 2\hat i + 2\hat j - a\hat k.$ The value of $a$ is

A

$-2$

B

$8$

C

$-7$

D

$-8$

Solution

(d) For perpendicular vector $\overrightarrow A.\overrightarrow B = 0$

$⇒$ $(5\hat i + 7\hat j – 3\hat k).(2\hat i + 2\hat j – a\hat k) = 0$

$⇒$ $10 + 14 + 3a = 0$$ \Rightarrow $ $a = – 8$

Standard 11

Physics

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