Question

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

• A. 45°
• B. 120°
• C. 150°
• D. 60°

Answer 1

Answer: (B)

120°

Answer 2

$R = \sqrt{A^{2} + B^{2} + 2AB\cos\theta}$

By substituting, $A = F,\mspace{6mu} B = F$ and $R = F$ we get

$\cos\theta = \frac{1}{2}\therefore\theta = 120{^\circ}$