how would you describe it in physics principles
hard stuff. check out on a search engine. that may help!
If you have a leak,drain the water out and use a propane torch and acid core solder. Wipe the solder joint with a baking soda water paste to neutralize the acid and not corrode the pipe.
Some of these would work without modification: rocket, ball and bat, nuclear fuel, pogo stick, swing, air bag, TNT, magnet, spray can, shot gun. Some are absolutely dependent on air pressure and cannot be modified to work without it: automobile, drinking straw, and some others.
