MCQ
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$-7$
- ✓$-8$
✓
Answer
Correct option: D.
$-8$
d
(d) For perpendicular vector $\overrightarrow A.\overrightarrow B = 0$
(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 $ $a = - 8$
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