A uniform metallic spherical shell is suspended from ceiling. It has two holes $A$ and $B$ at top and bottom respectively. Which of the following is/are true:-

If both the blocks as shown in the given arrangement are given together a horizontal velocity towards right. If $a_{\mathrm{cm}}$ be the subsequent acceleration of the centre of mass of the system of blocks then $a_{\mathrm{cm}}$ equals:-

Two persons $A$ and $B$ of weight $80 \mathrm{kg}$ and $50 \mathrm{kg}$ respectively are standing at opposite ends of a boat of mass $70 \mathrm{kg}$ and length $2 \mathrm{m}$ at rest. When they interchange their positions then displacement of the centre of mass of the boat will be:-

A small ball falling vertically downward with constant velocity $4 \mathrm{m} {\mathrm{s}}^{-1}$ strikes elastically a massive inclined cart moving with velocity $4 \mathrm{m} {\mathrm{s}}^{-1}$ horizontally as shown. The velocity of the rebound of the ball is:-

A particle of mass $4\mathrm{m}$ which is at rest explodes into four equal fragments. All $4$ fragments scattered in the same horizontal plane. Three fragments are found to move with velocity $v$ each as shown in the fig. The total energy relased in the process of explosion is:-

The diagram shows the velocity as a function of the time for an object with mass $10\mathrm{kg}$ being pushed along a frictionless surface by external force. At $t=3\mathrm{s}$, the force stops pushing and the object moves freely. It then collides head on and sticks to another object of mass $25\mathrm{kg}$:-