Man-ship model is a typical combination of explosion and completely inelastic collision.

When people jump from the first ship, the momentum is conserved, and the total mechanical energy suddenly soars, which is provided by human physical consumption and is the model of explosion; The characteristic of this model is that the total momentum remains constant all the time, but the internal non-mechanical energy is converted into mechanical energy, resulting in the relative speed of two or more parts.

But in any case, the vector sum of the component momentum of each part is always equal to the total momentum, and people fall into the second ship, and the momentum is conserved. However, people and ships form a completely inelastic collision, and the speed after the collision is equal, so that the total mechanical energy is converted into other energy in large quantities. This kind of collision has the largest loss of mechanical energy among all collisions with conservation of momentum, which is called completely inelastic collision.

Shapes such as bullets embedded in wood blocks, two wood blocks colliding and sticking together, magnets attracting each other, etc. Two objects with the same speed after collision are completely inelastic collisions.