Problem 1.34 prove p that in the absence of external forces, the total angular momentum (defined as l = α r α × p α ) of an n-particle system is conserved. [hints: you need to mimic the argument from (1.25) to (1.29). in this case you need more than newton’s third law: in addition you need to assume that the interparticle forces are central ; that is f αβ acts along the line joining particles α and β. a full discussion of angular momentum is given in chapter 3.]