A segment of angle $\mathrm{\theta }$ is cut from a half disc of symmetrically as shown. If the centre of mass of the remaining part is at a distance $a$ from $O$ and the centre of mass of the original disc was at distance $d$, then it can be definitely said that,

A small block of mass $\text{'}m\text{'}$ is placed on bigger block of mass $M\mathit{,}$ which is placed on a frictionless horizontal surface. The two blocks are given equal speed $u,$ but opposite directions, as shown in the figure. After some time, it is observed that both the blocks are moving in the direction of motion of the lower block, with a
speed greater than $\frac{u}{2}.$ It can be concluded that -

The diagram shows the velocity-time graph for two masses $R$ and $S$ that collided head on elastically. Which of the following statements is true?

$\mathrm{I}.$ $R$ and $S$ moved in the same direction after the collision.
$\mathrm{II}.$ The velocities of $R$ and $S$were equal at the mid-time of the collision.
$\mathrm{III}.$The mass of $R$ was greater than the mass of $S$.