Chapter 5

Newton′s Second Law of Motion

5.1 HOW A FORCE ALTERS THE MOMENTUM OF A PARTICLE

The last chapter taught us to view Newton′s First Law of motion from a broader perspective, namely conservation of linear momentum. Even when considering the motion of an isolated point particle (i.e., isolated from external influences) we would like to say that its momentum p remains constant in the absence of external forces (rather than repeat the Galilean version of the first law that a particle moves with constant velocity when no force is acting on it.)

What happens when the particle is subjected to external forces? By the very statement of the first law, the momentum of the particle must be changing with time. Therefore the first law serves as a qualitative ...

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