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 angle between $\hat a$ and $\hat b$ is $60^o$, then which of the following vector $(s)$ have magnitude one
$(A)$ $\frac{\hat a + \hat b}{\sqrt 3}$ $(B)$ $\hat a + \widehat b$ $(C)$ $\hat a$ $(D)$ $\hat b$
Two vectors having equal magnitudes of $x\, units$ acting at an angle of $45^o$ have resultant $\sqrt {\left( {2 + \sqrt 2 } \right)} $ $units$. The value of $x$ is
Two forces $P$ and $Q$, of magnitude $2F$ and $3F$, respectively, are at an angle $\theta $ with each other. If the force $Q$ is doubled, then their resultant also gets doubled. Then, the angle $\theta $ is ....... $^o$