Kinematics Question 303

Question: If $ |\vec{A}\times \vec{B}|=\sqrt{3}\vec{A}.\vec{B}, $ then the value of $ |\vec{A}+\vec{B}| $ it’s [CBSE PMT 2004]

Options:

A) $ \vec{A} $ and $ \vec{B} $ are perpendicular to each other

B) $ \vec{A} $ and $ \vec{B} $ act in the same direction

C) $ \vec{A} $ and $ \vec{B} $ act in the opposite direction

D) $ \vec{A} $ and $ \vec{B} $ can act in any direction

Show Answer

Answer:

Correct Answer: C

Solution:

$ \overrightarrow{A}.\overrightarrow{B}=AB\cos \theta $ In the problem $ \overrightarrow{A}.\overrightarrow{B}=-AB $ i.e. $ \cos \theta =-1 $ \ $ \theta =180{}^\circ $ i.e. $ \overrightarrow{A} $ and $ \overrightarrow{B} $ acts in the opposite direction.



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