Which of the following quantity/quantities are dependent on the choice of orientation of the co-ordinate axes?
$(a)$ $\vec{a}+\vec{b}$
$(b)$ $3 a_x+2 b_y$
$(c)$ $(\vec{a}+\vec{b}-\vec{c})$
Only $(b)$
Both $(a)$ and $(b)$
Both $(a)$ and $(c)$
Both $(b)$ and $(c)$
Two forces, each of magnitude $F$ have a resultant of the same magnitude $F$. The angle between the two forces is....... $^o$
A body is at rest under the action of three forces, two of which are ${\vec F_1} = 4\hat i,\,{\vec F_2} = 6\hat j,$ the third force is
If vectors $P, Q$ and $R$ have magnitude $5, 12$ and $13 $ units and $\overrightarrow P + \overrightarrow Q = \overrightarrow R ,$ the angle between $Q$ and $R$ is