Chapter 9 Linear Momentum and 93 collisions(碰撞) and Impulse(冲量) 1. Collision Collisions: in a collision, two bodies exert strong forces on each other for a relatively short time. This forces are internal to the two-body system and are significantly larger than any external force during the collision.Chapter 9 Linear Momentum and Collisions 9-3 collisions (碰撞) and Impulse (冲量) Collisions: in a collision, two bodies exert strong forces on each other for a relatively short time. 1. Collision This forces are internal to the two-body system and are significantly larger than any external force during the collision