Two forces, ${F_1}$ and ${F_2}$ are acting on a body. One force is double that of the other force and the resultant is equal to the greater force. Then the angle between the two forces is
${\cos ^{ - 1}}(1/2)$
${\cos ^{ - 1}}( - 1/2)$
${\cos ^{ - 1}}( - 1/4)$
${\cos ^{ - 1}}(1/4)$
If the sum of two unit vectors is a unit vector, then magnitude of difference is
Explain subtraction of vectors.
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
The resultant of two vectors $\overrightarrow P $ and $\overrightarrow Q $ is $\overrightarrow R .$ If $Q$ is doubled, the new resultant is perpendicular to $P$. Then $R $ equals