Which of the following represents a fully plastic collision? 1. two billiard balls hit each other then move in opposite directions. 2. two train cars hit then detach. 3. a ball hits a wall with no loss of energy. 4. a bullet hits a block and becomes embedded. 5. none of these.

Option (4)

Explanation:

There are two types of collision.

Perfectly elastic collision: the collision in which the momentum and kinetic energy is conserved. There is no loss of energy in other forms of energy.

Perfectly plastic collision: The collision in which the momentum is conserved and kinetic energy is not conserved. The two bodies stick after the collision.

Here, the bullet hits the block and then embedded in the block, it is the example of plastic collision.

thermal energy is the answer