3-1.Vectors
medium

दो सदिश $\mathop P\limits^ \to = a\hat i + a\hat j + 3\hat k$ तथा $\mathop Q\limits^ \to = a\hat i - 2\hat j - \hat k$ एक दूसरे के लम्बवत् हैं। $a$ का धनात्मक मान होगा

A

$3$

B

$4$

C

$9$

D

$13$

(AIIMS-2002)

Solution

(a) $\overrightarrow {\;P} .\overrightarrow {\;Q} = 0$

$⇒$  ${a^2} – 2a – 3 = 0$ $⇒$ $a = 3$

Standard 11
Physics

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