Kinematics Question 429
Question: It’s found that $ |A+B|=|A| $ . this necessarily implies.
Options:
A) $ B=0 $
B) $ \vec{A},\vec{B} $ antiparallel
C) $ \vec{A},\vec{B} $ are perpendicular
D) $ \vec{A}.\vec{B}\le 0 $
Correct Answer: B [b] $ (\vec{A}+\vec{B}).(\vec{A}+\vec{B})=\vec{A}.\vec{A} $
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Answer:
Solution:
$ \Rightarrow $ $ A^{2}+B^{2}+2\vec{A}.\vec{B}=A^{2} $
$ \Rightarrow $ $ 2\vec{A}.\vec{B}=-B^{2} $
