What happens to momentum in an inelastic collision?

In an inelastic collision, momentum is conserved but kinetic energy is not.

In physics, an inelastic collision is a type of collision where the colliding objects do not bounce away from each other completely. Instead, they may stick together or deform, and some of the kinetic energy is transformed into other forms of energy, such as heat or sound. However, the total momentum of the system before and after the collision remains the same. This is because momentum is always conserved in isolated systems, according to the law of conservation of momentum.

To understand this better, let's break it down. Momentum is a measure of the motion of an object and is calculated by multiplying the object's mass by its velocity. In an inelastic collision, even though the objects may change shape or stick together, the total momentum of the system (the sum of the momenta of all objects involved) before the collision is equal to the total momentum after the collision. This is because the forces involved in the collision are internal to the system, and internal forces do not change the total momentum of the system.

On the other hand, kinetic energy, which is the energy an object has due to its motion, is not conserved in an inelastic collision. Some of the kinetic energy is converted into other forms of energy, such as heat, sound, or potential energy due to deformation. This is why, after an inelastic collision, the total kinetic energy of the system is less than it was before the collision.

For example, if two cars collide and crumple together, they might move as a single unit after the collision. The momentum they had before the collision is now shared between them as a combined mass moving at a new velocity. However, some of the kinetic energy they had before the collision has been used to crumple the cars and generate heat and sound, so the total kinetic energy is reduced.