Neil deGrasse Tyson Explains the Physics of Collisions
Elastic and inelastic collisions are two types of interactions between objects in classical mechanics, distinguished by the conservation of kinetic energy.
Conservation of Momentum: The total momentum of the system before and after the collision remains constant.
Conservation of Kinetic Energy: The total kinetic energy of the system before and after the collision remains constant.
These conditions imply that no kinetic energy is transformed into other forms of energy, such as heat or sound, during the collision. Elastic collisions are typically idealized scenarios and are often approximated in collisions involving hard, non-deformable objects like billiard balls.
Example: Two identical billiard balls colliding head-on and bouncing back without any deformation or generation of heat.
In an inelastic collision:
Conservation of Momentum: The total momentum of the system before and after the collision remains constant.
Kinetic Energy Not Conserved: The total kinetic energy of the system before and after the collision is not the same. Some of the kinetic energy is converted into other forms of energy, such as heat, sound, or deformation energy.
Inelastic collisions are more common in real-world scenarios, where objects may deform or generate heat during the collision.
Example: A car crash where the vehicles crumple and generate heat, resulting in a loss of kinetic energy in the form of deformation and sound.
A perfectly inelastic collision is a specific type of inelastic collision where the colliding objects stick together after the impact, moving with a common velocity.
Example: A lump of clay thrown at another lump of clay where both lumps stick together and move as a single mass after the collision.
- Elastic Collision: Both momentum and kinetic energy are conserved.
- Inelastic Collision: Momentum is conserved, but kinetic energy is not conserved (some kinetic energy is converted into other forms of energy).
- Perfectly Inelastic Collision: An extreme form of inelastic collision where the objects stick together after colliding.
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