Most of us know that when you mix two substances together there’s no way of returning them to their original state. For example mixing some colors in water
This is true for non-viscous fluids. On the other hand, if the same thing is done with glycerine you will be able to return the fluids to their original state before mixing by simply un-mixing the fluids. This can happen because, unlike water, glycerine is a viscous fluid. The video below demonstrates this interesting phenomenon.
[MIT] 8.04 Quantum Physics I, Spring 2013 (Adams, Allan, Matthew Evans, & Barton Zwiebach) [Course home, Lecture videos]
This course covers the experimental basis of quantum physics. It introduces wave mechanics, Schrödinger’s equation in a single dimension, and Schrödinger’s equation in three dimensions. It is the first course in the undergraduate Quantum Physics sequence, followed by 8.05 Quantum Physics II and 8.06 Quantum Physics III.
I’ve been recently teaching Physics to 8th graders. We have finished the chapters on motion, forces, and friction, and just covered gravity. As part of this chapter, though not included in the curriculum or book, I introduced the concept of the free body diagram . In the first session introducing this concept, most students didn’t really grab what it is or why it is important.
For the last session before the vacation, I started the class by playing a video of the Ariane 5  launch that occurred on 29 August 2013 of the French Guiana:
Note: if can’t see the video click here.
In the Netherlands, some of the windmills used to drain the polders at Kinderdijk have been replaced by modern Archimedes screws.
Image by: M.A. Wijngaarden
License: CC Attribution-Share Alike 2.5 Generic license.