Q93 / 180 · NEET 2016 (Phase 1) · Physics

If the magnitude of sum of two vectors is equal to the magnitude of difference of the two vectors, the angle between these vectors is:

Solution

$|\vec{A} + \vec{B}| = |\vec{A} - \vec{B}|$

${\vec{A}}^{2} + {\vec{B}}^{2} + 2 |\vec{A}| |\vec{B}| \cos θ = {\vec{A}}^{2} + {\vec{B}}^{2} - 2 |\vec{A}| |\vec{B}| \cos θ$

$4 |\vec{A}| |\vec{B}| \cos θ =0$

$\cos θ = 0$

$θ = 90 °$

Hence, the correct answer is option: 'B'.