* Momentum is a measure of an object's mass in motion. It's calculated as mass times velocity (p = mv).

* Objects can lose momentum in several ways:

* Applying a force: A force can change an object's velocity, which directly affects its momentum. Think of a car braking – it loses momentum due to the friction force from the brakes.

* Collisions: When objects collide, they can transfer momentum to each other. The total momentum of the system (all objects involved) remains constant, but individual objects may gain or lose momentum.

* External forces: Gravity, friction, and air resistance are examples of external forces that can change an object's momentum.

The key concept is the law of conservation of momentum:

* In a closed system (no external forces), the total momentum remains constant, even if individual objects within the system exchange momentum.

So, while momentum itself isn't lost, an object can lose momentum if:

* It interacts with other objects or forces.

* It's part of a system where momentum is transferred between components.