question_answer

When is the magnitude of the resultant of two vectors equal to either of them?

Answer:

                When two vectors of equal magnitude are inclined to each other at an angle of\[\text{12}0{}^\circ \], the magnitude of their resultant is equal to that of the either vector. \[{{a}^{2}}={{a}^{2}}+{{a}^{2}}+2{{a}^{2}}{{\cos }^{2}}\theta \] \[\Rightarrow \cos \theta =-\frac{1}{2}\]\[\Rightarrow \]              \[\theta ={{120}^{\circ }}\]