The resultant of two forces, one double the other in magnitude, is perpendicular to the smaller of the two forces. The angle between the two forces is ........ $^o$
Two forces with equal magnitudes $F$ act on a body and the magnitude of the resultant force is $F/3$. The angle between the two forces is
If $\vec{P}+\vec{Q}=\vec{P}-\vec{Q}$, then
The magnitudes of vectors $\vec A,\,\vec B$ and $\vec C$ are $3, 4$ and $5$ units respectively. If $\vec A + \vec B = \vec C$, the angle between $\vec A$ and $\vec B$ is