assorted solutions:

Double pendulum (Q1): https://www.youtube.com/watch?v=neh86u7_TIk

Perturbation theory (Q2): http://physicspages.com/pdf/Griffiths%20QM/Griffiths%20Problems%2006.01.pdf

http://physicspages.com/pdf/Griffiths%20QM/Griffiths%20Problems%2006.04.pdf

Ehrenfest theorem (Q3c):

https://www.youtube.com/watch?v=dWCVHyFOn8w&list=LL52kszkc08-acFOuogFl5jw

Spin (Q3d):

http://physicspages.com/pdf/Griffiths%20QM/Griffiths%20Problems%2004.28.pdf

Special relativity (Q4):

https://www.astro.umd.edu/~miller/teaching/astr498/srpractice.pdf

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