PHYSICS: Our discussion of pendulums seems to have disappeared, so here are a few old vodcasts on simple harmonic motion that might help. The first vodcast below concentrates on spring. The second concentrates on pendulums. The third is a look at an old spring problem.

Simple Harmonic Motion & Springs

Photo by Becca Romine on Unsplash

Simple Harmonic Motion & the Pendulum

flickr photo by sudip