Hat tip to Frank for sending me a link to this video:
If you have never done a demo like this (without the motorcycle), you should. It really isn't too difficult. Here is a video of my version:
Inertial demo from Rhett Allain on Vimeo.
So, the question is: is the motorcycle thing real or fake?
First, let me talk about the key aspect of this demo. Why don't the glasses move? Well, they move - but just not very far. The demo is supposed to be an example of Newton's Second law, or you could say it is the momentum principle (which is what I will use). If a force is applied for a short time…