Vectors Question 34

Question: If $ |,\vec{A}+\vec{B},|,=,|,\vec{A},|+|,\vec{B},| $ , then angle between $ \vec{A} $ and $ \vec{B} $ will be

[CBSE PMT 2001]

Options:

A) $ 90{}^\circ $

B) $ 120{}^\circ $

C) $ 0{}^\circ $

D) $ 60{}^\circ $

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Answer:

Correct Answer: C

Solution:

Resultant of two vectors $ \overrightarrow{A} $ and $ \overrightarrow{B} $ can be given by $ \overrightarrow{R}=\overrightarrow{A}+\overrightarrow{B} $

$ |\overrightarrow{R}|,=,|\overrightarrow{A}+\overrightarrow{B}|,=\sqrt{A^{2}+B^{2}+2AB\cos \theta } $ If $ \theta =0{}^\circ $ then $ |\overrightarrow{R}|,=A+B $

$ =,|\overrightarrow{A}|+|\overrightarrow{B}| $