- Home
- Standard 11
- Physics
3-1.Vectors
easy
When $\vec A.\vec B = - |A||B|,$ then
A
$\vec A$ and $\vec B$ are perpendicular to each other
B
$\vec A$ and $\vec B$ act in the same direction
C
$\vec A$ and $\vec B$ act in the opposite direction
D
$\vec A$ and $\vec B$ can act in any direction
Solution
(c) $\overrightarrow A .\overrightarrow B = AB\cos \theta $
In the problem $\overrightarrow A .\overrightarrow B = – AB$ i.e. $\cos \theta = – 1$
$\theta = 180^\circ $
i.e. $\overrightarrow A $ and $\overrightarrow B $ acts in the opposite direction.
Standard 11
Physics
Similar Questions
If $\theta$ is the angle between two vectors $A$ and $B$, then match the following two columns.
| colum $I$ | colum $II$ |
| $(A)$ $A \cdot B =| A \times B |$ | $(p)$ $\theta=90^{\circ}$ |
| $(B)$ $A \cdot B = B ^2$ | $(q)$ $\theta=0^{\circ}$ or $180^{\circ}$ |
| $(C)$ $|A+B|=|A-B|$ | $(r)$ $A=B$ |
| $(D)$ $|A \times B|=A B$ | $(s)$ None |
medium
