MCQ
Let the angle between two nonzero vectors $\overrightarrow A $ and $\overrightarrow B $ be $120^°$ and resultant be $\overrightarrow C $
  • A
    $\overrightarrow C $ must be equal to $|\overrightarrow A - \overrightarrow B |$
  • B
    $\overrightarrow C $ must be greater than $|\overrightarrow A - \overrightarrow B |$
  • $\overrightarrow C $ must be less than $|\overrightarrow A - \overrightarrow B |$
  • D
    $\overrightarrow C $ may be equal to $|\overrightarrow A - \overrightarrow B |$

Answer

Correct option: C.
$\overrightarrow C $ must be less than $|\overrightarrow A - \overrightarrow B |$
c
(c) If $\overrightarrow{\mathrm{C}}$ is resultant of $\overrightarrow{\mathrm{A}}$ and $\overrightarrow{\mathrm{B}}$, then

$|\overrightarrow{\mathrm{C}}|=\sqrt{\mathrm{A}^{2}+\mathrm{B}^{2}+2 \mathrm{AB} \cos 120^{\circ}}$

$|\overrightarrow{\mathrm{C}}|=\sqrt{\mathrm{A}^{2}+\mathrm{B}^{2}-\mathrm{AB}} \quad\left[\text { Ascos } 120^{\circ}=-\frac{1}{2}\right]$

similarly, $|\overrightarrow{\mathrm{A}}-\overrightarrow{\mathrm{B}}|=\sqrt{\mathrm{A}^{2}+\mathrm{B}^{2}-2 \mathrm{AB} \cos 120^{\circ}}$

$=\sqrt{A^{2}+B^{2}+A B}$

$|\overrightarrow{\mathrm{A}}-\overrightarrow{\mathrm{B}}|>\mathrm{C}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

A capillary tube of radius $r$ is immersed in water and water rises in it to a height $h$. The mass of water in the capillary tube is $5\,g$. Another capillary tube of radius $2r$ is immersed in water. The mass of water that will rise in this tube is ...... $g$
If the absorption and reflection co-efficients of a surface of a body are $0.4$ and $0.6$ respectively, then
Error in the measurement of radius of a sphere is $0.2\%$. The error in the calculated value of its volume is  ......... $\%$
The equation of $SHM$ of a particle is given as

$2\,\frac{{{d^2}x}}{{d{t^2}}} + 32x = 0$

where $x$ is the displacement from the mean position of rest. The period of its oscillation (in seconds) is

In an isothermal process on an ideal gas, the pressure increases by 0.5%. The volume decreases by about
  1. 0.25%
  2. 0.5%
  3. 0.7%
  4. 1%​​
One mole of an ideal monoatomic gas undergoes the following four reversible processes:

Step $1$ It is first compressed adiabatically from volume $V_{1}$ to $1 \;m ^{3}$.

Step $2$ Then expanded isothermally to volume $10 \;m ^{3}$.

Step $3$ Then expanded adiabatically to volume $V _{3}$.

Step $4$ Then compressed isothermally to volume $V_{1}$. If the efficiency of the above cycle is $3 / 4$, then $V_{1}$ is ............ $m^3$

Match list-$I$ with list-$II$:

List-$i$ List-$2$
$(A)$Kinetic energy of plant  $(1)$ $-\frac{\mathrm{GMm}}{\mathrm{a}}$
$(B)$ Gravaitatioin  potentiyal energy of sun -plant system  $(2)$ $\frac{\mathrm{GMm}}{2 \mathrm{a}}$ 
$(C)$Total mecaniacal energy of palnt  $(3)$ $\frac{\mathrm{Gm}}{\mathrm{r}}$
$(D)$Escap energyat the surface of plant for unit mass object $(4)$ $-\frac{\mathrm{GMm}}{2 \mathrm{a}}$

(Where $\mathrm{a}=$ radius of planet orbit, $\mathrm{r}=$ radius of planet, $M=$ mass of Sun, $m=$ mass of planet)

Choose the correct answer from the options given below:

A body weighs $700 \,gm$ wt on the surface of the earth. How much will it weigh on the surface of a planet whose mass is $\frac{1}{7}$ and radius is half that of the earth ........ $gm\, wt$
A boggy of uniformly moving train is suddenly detached from train and stops after covering some distance. The distance covered by the boggy and distance covered by the train in the same time has relation
Water is flowing through a horizontal pipe of non-uniform cross-section. At the extreme narrow portion of the pipe, the water will have