$A$ bullet hits and gets embedded in a solid block resting on a horizontal frictionless table. What is conserved?

Statement $1$: In a perfectly inelastic collision,the total energy of two particles moving in the same direction is not completely lost.
Statement $2$: The principle of conservation of momentum is valid for all types of collisions.

In a one-dimensional collision, a particle of mass $2m$ collides with a particle of mass $m$ at rest. If the particles stick together after the collision, what fraction of the initial kinetic energy is lost in the collision?

$A$ 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 .......... $J$.

$A$ body of mass $3 \ kg$ moving with a velocity $(2 \hat{i}+3 \hat{j}+3 \hat{k}) \ m/s$ collides with another body of mass $4 \ kg$ moving with a velocity $(3 \hat{i}+2 \hat{j}-3 \hat{k}) \ m/s$. The two bodies stick together after collision. The velocity of the composite body is

When does the total kinetic energy of two bodies moving in opposite directions become zero after a collision?