In an orbital motion, the angular momentum vector is 

1. Along the radius vector

2. Parallel to the linear momentum

3. In the orbital plane

4. Perpendicular to the orbital plane

A particle of mass $m$ moves with a constant velocity along $3$ different paths, $DE, OA$ and $BC$. Which of the following statements is not correct about its angular momentum about point $O$?

$\mathrm{A} \mathrm{particle} \mathrm{of} \mathrm{mass} 0.2 \mathrm{kg} \mathrm{is} \mathrm{moving} \mathrm{in} \mathrm{a} \mathrm{circle} \mathrm{of} \mathrm{radius} 1\mathrm{m} \mathrm{with}$
$\mathrm{f}=2/\mathrm{\pi } \mathrm{rps}, \mathrm{then} \mathrm{its} \mathrm{angular} \mathrm{momentum} \mathrm{is}-$
$\left(\mathrm{A}\right) 0.8 {\mathrm{kgm}}^2/\mathrm{s} \left(\mathrm{B}\right) 2 {\mathrm{kgm}}^2/\mathrm{s}$
$\left(\mathrm{C}\right) 8 {\mathrm{kgm}}^2/\mathrm{s} \left(\mathrm{D}\right) 16 {\mathrm{kgm}}^2/\mathrm{s}$

In free space, a rifle of mass $M$ shoots a bullet of mass $m$ at a stationary block of mass $M$ at a distance $D$ away from it. When the bullet has moved through a distance $d$ towards the block, the centre of mass of the bullet-block system is at a distance of:
1. $\frac{D-d}{M+m}~\text{from the bullet}$
2. $\frac{md+ MD}{M+m}~\text{from the block}$
3. $\frac{2md+ MD}{M+m}~\text{from the block}$
4. $\frac{(D-d)M}{M+m}~\text{from the bullet}$

Blocks A and B are resting on a smooth horizontal surface given equal speeds of 2 m/s in the opposite sense as shown in the figure.

At t = 0, the position of blocks are shown, then the coordinates of centre of mass at t = 3s will be 

1.  (1, 0)

2.  (3, 0)

3.  (5, 0)

4.  (2.25, 0)

A wheel is at rest. Its angular velocity increases uniformly and becomes 80 rad/s after 5 s. The total angular displacement is 

1. 800 rad

2. 400 rad

3. 200 rad

4. 100 rad

Moment of inertia of an object does not depend upon

A force $\overrightarrow{\mathrm{F}} = 4\hat{\mathrm{i}} - 5\hat{\mathrm{j}} + 3\hat{\mathrm{k}}$ is acting on a point $\overrightarrow{{\mathrm{r}}_1} = \hat{\mathrm{i}} + 2\hat{\mathrm{j}} + 3\hat{\mathrm{k}}$. The torque acting about a point $\overrightarrow{{\mathrm{r}}_2} = 3\hat{\mathrm{i}} - 2\hat{\mathrm{j}} - 3\hat{\mathrm{k}}$ is

1.  0

2.  $42\hat{\mathrm{i}} - 30\hat{\mathrm{j}} + 6\hat{\mathrm{k}}$

2.  $42\hat{\mathrm{i}} + 30\hat{\mathrm{j}} + 6\hat{\mathrm{k}}$

4.  $42\hat{\mathrm{i}} + 30\hat{\mathrm{j}} - 6\hat{\mathrm{k}}$

A thin uniform circular disc of mass $M$ and radius $R$ is rotating in a horizontal plane about an axis passing through its center and perpendicular to its plane with an angular velocity $\omega$. Another disc of the same dimensions but of mass $\frac{1}{4}M$ is placed gently on the first disc co-axially. The angular velocity of the system will be: