In perfectly inelastic collisions,the relative velocity of the bodies

$A$ mass $M$ moving with velocity $V$ along the $x$-axis collides and sticks to another mass $2M$ which is moving along the $y$-axis with velocity $3V$. The velocity of the combination after the collision is:

$A$ body of mass $3 \,kg$ is moving with a velocity of $8 \,ms^{-1}$ collides head-on with another body of mass $1 \,kg$, moving in the opposite direction with a velocity of $4 \,ms^{-1}$. After the collision, if the two bodies stick together and move, they move with a common velocity: (in $\,ms^{-1}$)

$A$ bullet of mass $m$ travelling with a speed $v$ hits a block of mass $M$ initially at rest and gets embedded in it. The combined system is free to move and there is no other force acting on the system. The heat generated in the process will be

$A$ body of mass $10 \, kg$ moving with a speed of $3 \, m/s$ collides with another stationary body of mass $5 \, kg$. As a result,the two bodies stick together. The $KE$ of the composite mass will be .......... $J$.

$A$ bullet of mass $a$ moving with velocity $b$ strikes a block of mass $c$ and gets embedded in it. Find the velocity of the block.