Kinematics Question 588
Question: If $ A=5\widehat{i}+7\widehat{j}-3\widehat{k} $ and $ B=2\widehat{i}+2\widehat{j}-a\widehat{k} $ are perpendicular vectors, the value of a is:
Options:
A) $ -2 $
B)8
C) $ -7 $
D)$ -8 $
Show Answer
Answer:
Correct Answer: D
Solution:
[d] $ \vec{A}\text{.}\vec{B}\text{=}\text{0} $
$ \text{or }( 5\hat{i}+7\hat{j}-3\hat{k} ).( 2\hat{i}+2\hat{j}-a\hat{k} )=0 $
$ \therefore 5\times 2+7\times 2+3a=0ora=-8 $
