${\vec A }$, ${\vec B }$ and ${\vec C }$ are three non-collinear, non co-planar vectors. What can you say about directin of $\vec A \, \times \,\left( {\vec B \, \times \vec {\,C} } \right)$ ?
The direction of $(\vec{B} \times \vec{C})$ will be perpendicular to the plane containing $\vec{B}$ and $\vec{C}$. $\vec{A} \times(\vec{B} \times \vec{C})$ will lie in the plane of $\vec{B}$ and $\vec{C}$ and is perpendicular to $\vec{A}$.
Explain the geometrical interpretation of scalar product of two vectors.
If $\left| {\vec A } \right|\, = \,2$ and $\left| {\vec B } \right|\, = \,4$ then match the relation in Column $-I$ with the angle $\theta $ between $\vec A$ and $\vec B$ in Column $-II$.
Column $-I$ | Column $-II$ |
$(a)$ $\left| {\vec A \, \times \,\,\vec B } \right|\, = \,\,0$ | $(i)$ $\theta = \,{30^o}$ |
$(b)$ $\left| {\vec A \, \times \,\,\vec B } \right|\, = \,\,8$ | $(ii)$ $\theta = \,{45^o}$ |
$(c)$ $\left| {\vec A \, \times \,\,\vec B } \right|\, = \,\,4$ | $(iii)$ $\theta = \,{90^o}$ |
$(d)$ $\left| {\vec A \, \times \,\,\vec B } \right|\, = \,\,4\sqrt 2$ | $(iv)$ $\theta = \,{0^o}$ |
Colum $I$ | Colum $II$ |
$(A)$ $(A+B)$ | $(p)$ North-east |
$(B)$ $(A-B)$ | $(q)$ Vertically upwards |
$(C)$ $(A \times B)$ | $(r)$ Vertically downwards |
$(D)$ $(A \times B) \times(A \times B)$ | $(s)$ None |
Let $\left| {{{\vec A}_1}} \right| = 3,\,\left| {\vec A_2} \right| = 5$, and $\left| {{{\vec A}_1} + {{\vec A}_2}} \right| = 5$. The value of $\left( {2{{\vec A}_1} + 3{{\vec A}_2}} \right)\cdot \left( {3{{\vec A}_1} - 2{{\vec A}_2}} \right)$ is