Question

Square of the resultant of two forces of equal magnitude is equal to three times their product.The angle between them is :-

• A. $0^{\circ }$
• B. ${45}^{\circ }$
• C. ${60}^{\circ }$
• D. ${90}^{\circ }$

Answer 1

The correct option is C ${60}^{\circ }$

Let the vectors be $\overrightarrow{A}$ and $\overrightarrow{B}$, each with magnitude A.
According to condition in question resultant $R=3A^2$
Given: $A^2+A^2+2A.A.cos\theta =3A^2$
Thus, $A^2=2A^{2}cos\theta$ or $cos\theta =1/2$

Hence, $\theta ={60}^0$