Kinematics Question 424

Question: The vector $ \vec{P}=a\hat{i}+a\hat{j}+3\hat{k} $ and $ \vec{Q}=a\hat{i}-2\hat{j}-\hat{k} $ are perpendicular to each other. The positive value of a is

Options:

A) 3

B) 4

C) 9

D) 13

Show Answer

Answer:

Correct Answer: A

Solution:

[a] $ \overrightarrow{P}.\overrightarrow{Q}=0 $

$ \Rightarrow $ $ a^{2}-2a-3=0 $

$ \Rightarrow $ $ a=3 $



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