Chapter 4.3, Problem 4.23P

(a)

To determine

To prove that $\frac{d}{dt}\langle \text{L}\rangle =\langle \text{N}\rangle$ for a particle in a potential $V\left(r\right)$.

(b)

To determine

To show that $\frac{d\langle \text{L}\rangle }{dt}=0$ for any spherically symmetrical potential.