14.4 : 입자 시스템의 선형 운동량 보존

In a game of billiards, when the cue ball strikes a stationary ball, it transfers some of its momentum to the stationary ball. The cue ball slows down, and the struck ball starts moving.

The impulsive force acting on the ball is for a very short duration. So its impulse can be neglected.

When the sum of external impulses acting on a system of particles is zero, the principle of linear impulse and momentum simplifies, representing the conservation of linear momentum. This principle is commonly applied when particles collide or interact.

In impulse-momentum analysis, forces can be impulsive or non-impulsive.

Impulsive forces act briefly yet cause substantial momentum changes. For instance, the forceful impact of a moving ball on a stationary one in billiards leads to immediate momentum change for both balls.

Conversely, non-impulsive forces operate over longer periods compared to the time of the collision, such as the friction between balls and the table. Though slightly affecting momentum, their impact is minor compared to collision forces.