Kinematics Question 432

Question: The resultant of $ \vec{A} $ and $ \vec{B} $ it’s $ {{\vec{R}}_1} $ . On reversing the vector $ \vec{B}, $ the resultant becomes $ {{\vec{R}}_2} $ . What is the value of $ R_1^{2}+R_2^{2}? $

Options:

A) $ A^{2}+B^{2} $

B) $ A^{2}-B^{2} $

C) $ 2(A^{2}+B^{2}) $

D) $ 2(A^{2}-B^{2}) $

Show Answer

Answer:

Correct Answer: C

Solution:

[c] $ R_1^{2}=A^{2}+B^{2}+2AB\cos \theta $

$ R_2^{2}=A^{2}+B^{2}-2AB\cos \theta $
$ \therefore $ $ R_1^{2}+R_2^{2}=2(A^{2}+B^{2}) $



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