Conservation of Linear Momentum, Collisions

Conservation of Linear Momentum

Linear momentum is a vector quantity calculated as the product of an object’s mass and velocity.
The principle of conservation of linear momentum states that the total momentum of a closed system of objects (one that does not exchange matter or energy with its surroundings) remains constant, providing no external forces act on it.
Linear momentum is conserved in all directions, not just the direction of motion.

Momentum and Collisions

Collisions illuminate the principle of conservation of momentum particularly well. A collision is an interaction between two bodies in which the two bodies come in contact.
In simple terms, the total momentum before a collision equals the total momentum after a collision.
A collision can be categorised as either elastic or inelastic.

Elastic Collisions

In an elastic collision, both momentum and kinetic energy are conserved.
No energy is lost in the form of heat, sound, etc.
Examples of almost perfect elastic collisions include collisions between gas molecules or billiard balls.

Inelastic Collisions

In an inelastic collision, momentum is conserved but kinetic energy is not.
Some of the kinetic energy is converted into other forms, such as heat or sound.
Most real-world collisions are inelastic, with the extreme case known as a perfectly inelastic collision, where the two bodies stick together after impact.

Impulse and Change in Momentum

The change in momentum of an object is equal to the impulse imparted to it, which is the product of the force applied to it and the time period during which the force is applied.
The greater the impulse, the greater the change in momentum, meaning greater force or more time can have a significant effect on the object’s motion.
This principle is applied in many real-world contexts, such as technology behind crumple zones in cars and padding in helmets.

Applications in Physics

Knowledge of momentum and its conservation can be used to predict the result of a collision.
It forms the basis for the study of many fundamental phenomena in physics, including rocket propulsion and nuclear reactions.
Understanding the concept of linear momentum is critical for a broad range of scientific and engineering disciplines, including mechanics, electromagnetism, and quantum physics.