We are always trying to relate what we teach in class to practical examples but its not always easy. Cars don't have uniform acceleration and rubber tyres don't obey the equation F= μN. Today I showed two youtube videos to illustrate how the electric field inside a hollow sphere was zero, one from Topgear about testing a car under a high voltage power line and a heavy metal band that uses a Tesla coils as part of their performance. Neither of these are spheres. This afternoon I was with 4 of my Physics students at a cliff instructing young children in rock climbing. It's part of the CAS program. To make life easy we leave a thin line threaded through the anchor at the top of the cliff so we can pull up a climbing rope without having to climb to the top. This can be problematic when the knot has to be pulled through the karabiner. The way to do it is to flick the rope sending a wave upwards, if the line is pulled just as the wave gets to the top then the knot will pull through. As you can see in the video this requires a certain amount of timing.