Download App

STD 11 - 6. system of particles and rotational motion — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 11 - 6. system of particles and rotational motion4 Marks
MCQ
If force $\vec{F}=3 \hat{i}+4 \hat{j}-2 \hat{k}$ acts on a particle having position vector $2 \hat{i}+\hat{j}+2 \hat{k}$ then, the torque about the origin will be
  • A
    $3 \hat{ i }+4 \hat{ j }-2 \hat{ k }$
  • ✓
    $-10 \hat{ i }+10 \hat{ j }+5 \hat{ k }$
  • C
    $10 \hat{ i }+5 \hat{ j }-10 \hat{ k }$
  • D
    $10 \hat{ i }+\hat{ j }-5 \hat{ k }$
✓

Answer

Correct option: B.
$-10 \hat{ i }+10 \hat{ j }+5 \hat{ k }$
b
$\vec{\tau}=\vec{r} \times \vec{F}$

$=\left|\begin{array}{ccc}\hat{i} & \hat{j} & \hat{k} \\ 2 & 1 & 2 \\ 3 & 4 & -2\end{array}\right|$

$=\hat{\hat{i}}(-2-8)-\hat{ j }(-4-6)+\hat{ k }(8-3)$

$=-10 \hat{ i }+10 \hat{ j }+5 \hat{ k }$

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

Explore more

JEE STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

The $X-$ ray wavelength of ${L_\alpha }$ line of platinum $(Z=78)$ is $1.30\,{Å}.$ The $X -$ ray wavelength of ${L_\alpha }$ line of Molybdenum $(Z=42)$ is .............. $\mathop {\rm{A}}\limits^o $
→
During lighting, a current pulse, shown in figure, flows from the cloud at a height $1.5\ km$ to the ground. If the breakdown electric field of humid air is about $400\ kVm^{-1}$ , the energy released during lighting would be (in unit of $10^9\ J$ )
→
The figure shows a velocity-time graph of a particle moving along a straight line  The total distance travelled by the particle is  ........ $m$
→
Two skaters $A$ and $B$ of weights in the ratio $5 : 7$ start facing each other $6\,metres$ apart on a horizontal smooth surface. They pull on a rope stretched between them. How far has each moved when they meet?
→
Two satellites $A$ and $B$ having masses in the ratio $4: 3$ are revolving in circular orbits of radii $3\,r$ and $4\,r$ respectively around the earth. The ratio of total mechanical energy of $A$ to $B$ is.
→
In the given circuit, an ideal voltmeter connected across the $10\,\Omega $ resistance reads $2\, V$. The internal resistance $r$, of each cell is ................... $\Omega$
→
Which of the following rays has the maximum frequency
→
An elevator weighing $6000\, kg$ is pulled upward by a cable with an acceleration of $5\,m{s^{ - 2}}$. Taking g to be $10\,m{s^{ - 2}}$, then the tension in the cable is ........... $N$
→
The Bulk modulus for an incompressible liquid is
→
At time $t = 0$, a simple harmonic oscillator is at its extreme position. If it covers half of  the amplitude distance in $1\, second$, then the time period of oscillation is ..... $s$
→