Differentiate between elastic and inelastic collisions.

Elastic collisions conserve both momentum and kinetic energy, while inelastic collisions conserve momentum but not kinetic energy.

In physics, collisions are categorised into two types: elastic and inelastic. The primary difference between these two types of collisions lies in the conservation laws. In an elastic collision, both momentum and kinetic energy are conserved. This means that the total momentum and total kinetic energy before the collision are equal to the total momentum and total kinetic energy after the collision. Elastic collisions are often observed in atomic and subatomic particles, where the forces during collision are conservative.

In contrast, in an inelastic collision, only momentum is conserved while kinetic energy is not. The total kinetic energy of the system before the collision is greater than the total kinetic energy after the collision. The lost kinetic energy is usually converted into other forms of energy such as heat, sound, or deformation energy. Inelastic collisions are common in our daily life, for example, when a ball hits the ground and doesn't bounce back to its original height, or when two cars collide and get dented.

It's important to note that the conservation of momentum applies to both types of collisions. Momentum, a vector quantity, is the product of an object's mass and velocity. The total momentum of a closed system (one that doesn't interact with external forces) remains constant, regardless of the nature of the collisions happening within it.

In summary, the key difference between elastic and inelastic collisions is the conservation of kinetic energy. In an elastic collision, both momentum and kinetic energy are conserved, meaning the total amounts before and after the collision remain the same. In an inelastic collision, while momentum is conserved, kinetic energy is not, with some of it being converted into other forms of energy.