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3-1.Vectors
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જો બે સદિશો $\overrightarrow{ P }=\hat{i}+2 m \hat{j}+m \hat{k}$ અને $\vec{Q}=4 \hat{i}-2 \hat{j}+m \hat{k}$ પરસ્પર લંબ હોય, તો $m$ નું મૂલ્ય ........ હશે.
A
$1$
B
$-1$
C
$-3$
D
$2$
(JEE MAIN-2023)
Solution
$\overrightarrow{ P } \cdot \overrightarrow{ Q }=0$
$(\hat{i}+2 m \hat{j}+m \hat{k}) \cdot(4 \hat{i}-2 \hat{j}+m \hat{k})=0$
$\Rightarrow 4-4 m+m^2=0$
$\Rightarrow( m -2)^2=0 \Rightarrow m=2$
Standard 11
Physics