When a bullet is fired from a gun, its kinetic energy is initially high due to its velocity. Upon striking the sand wall, the bullet penetrates and eventually stops. The kinetic energy of the bullet is converted into several forms of energy. Primarily, it is transformed into heat energy, which is absorbed by the bullet, the sand, and the surrounding air. Additionally, some energy is used in doing work to deform the sand and the bullet. There is also a small amount of energy lost as sound during the collision. All of the bullet’s kinetic energy dissipates in these ways, and none remains in the bullet once it stops.