Applications of recoil principle in classical physics Are there any interesting, important or (for the non physicist) astonishing examples where the recoil principle (as special case of conservation of linear momentum) is applied beside rockets and guns?
I am teaching physics in high school and was just wondering if there are any more interesting examples than the two textbook standard examples above. 
I am not interested in examples which are not in the domain of macroscopic, classical physics like Mößbauer-effect or something like that.
 A: Super-simple rocket propulsion is easy to do:


*

*stand on a red wagon and throw weights off it in one direction

*put a garden hose with a nozzle against a scale and turn it on. It will generate thrust.

*one I've wanted to try but haven't had the nerve: sit on a bicycle and use a hand-held leaf blower as propulsion.

*you can buy rockets that consist of a water bottle and an air pump. The hard part is finding them afterward.

*one of my favorites (though not really a rocket) is an Astro-Blaster. They're easy to make. Just stack up rubber balls in weight ratios 1/3, 2/4, 3/5, ..., as many as you want.
If you stack up N of them and drop them (carefully, in a line) they will all stay on the surface, except the top one, which will bounce to $N^2$ the height you dropped them from (ideally). It really gets attention.
A: The most astonishing application for me is ablation pressure: when you shine a gas of high energy X-rays onto a material, the material will eject particles outward off the surface, and the outgoing ejected particles make a reaction pressure on the material, which compresses the remaining stuff. This ablation pressure is critical for getting implosion in the infamous Teller-Ulam design (see here: http://en.wikipedia.org/wiki/Teller%E2%80%93Ulam_design).
A: Yarkovsky effect (almost like a photon rocket, I think).
Non-uniform thermal radiation (because 'day' is hotter than 'night') of a celestial object can give a net recoil. More spoiler:
http://en.wikipedia.org/wiki/Yarkovsky_effect
A: The sudden recoil of a DC motor when it starts rotating. See: http://arxiv.org/abs/0710.2155  It contains analysis of this and other examples.
