The discussion centers on the conservation of angular momentum as it relates to Newton's third law of motion, specifically in systems of particles. It is established that while action and reaction forces are equal and opposite, they do not necessarily lie along the line connecting the particles, which is crucial for the conservation of angular momentum. The total angular momentum of a system is conserved only when external torque is absent. The conversation highlights that in idealized cases of contact forces, conservation holds true regardless of the perspective, particularly in collision scenarios.
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Of course, in the special (&idealized) case of CONTACT forces, the joining line segment is of zero length, and hence, the conservation of total angular momentum is preserved anyhow we look at it...Shooting star said:I don't have the book right now with me, so I'm a bit unsure of exactly what you don't like. I presume that you are talking about system of particles. The third law states that the action and reaction forces are equal and opposite, but does not say that they lie along the line joining the particles. Only in the latter case will the total angular momentum of a system be conserved if the external torque is zero.
That's a typical case, yes.Shooting star said:So, the case you are talking about is more pertinent for collisions, it seems to me?