Vectors Question 7

Question: Two forces, each of magnitude F have a resultant of the same magnitude F. The angle between the two forces is

[CBSE PMT 1990]

Options:

A) $ 45{}^\circ $

B) $ 120{}^\circ $

C) $ 150{}^\circ $

D) $ 60{}^\circ $

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Answer:

Correct Answer: B

Solution:

$ R=\sqrt{A^{2}+B^{2}+2AB\cos \theta } $ By substituting, $ A=F,\ B=F $ and $ R=F $ we get $ \cos \theta =\frac{1}{2}\

Therefore \theta =120{}^\circ $