Tony et al., I've tried to duplicate the 'Moss Effect' using four different nozzles, and buckets ranging from nominal 3 gallon (U.S., not Imperial) down to less than 1 gallon capacities. At no time did I observe anything I could interpret as reversal of the 'reaction effect.' All 4 nozzles were of the sort with a tapered central spindle adjustable in relation to a coaxial orifice. I.e their jet-forming arrangement appears to agree, at least in general type, to Tony's description:
" * The nozzle is one of those variable things which screw back and forth around a central pin. The 'single jet' is more of a tight spray pattern really." 2 of my 4 nozzles are of 'pistol grip' configuration, with the 'handle' portion an inline coupling to the hose (Eng. hose- pipe) and the jet forming part directed at an angle of about 60° to the handle/hose axis. When the hose is gripped a foot or so back from the nozzle fitting, and the spray dirrected perpendicular to the water surface, the cantilevered hose segment acts as a crude spring-balance. In the case of the 'straight on' nozzles, the redirection of the hose from a roughly horizontal algnment to have the jet impinge normal to the water surface was less well defined, while sensing changes in the apparent reaction force depends upon details of this configuration, and on kinesthetic assessment and 'muscle memory' to compare reaction forces. Tony recently wrote: "In hindsight I'm glad I was quite specific in describing the water 'jet' in my experiments. viz/ a tightly-concentrated stream of droplets rather than a 'solid' stream of water as John seems to have isolated this as a possible 'culprit'. " In my experiments, I tried nozzle settings ranging from a widely- conical, fine droplet, 'mist,' to a very solid, compact, stream (as seen in free air.) Some confounding factors that have not yet been mentioned in this thread: 1) With no nozzle present (and no constriction at the coupling fitment) there is no acceleration or reaction exerted by the outflow at the hose's end. 2) There is, however, a reaction to the effect of curvature in the hose. I. e. for an assumed circular arc segment, there is a centripetal acceleration, and accordingly a centrifugal force exerted on the hose wall at the outside of the curve, which appears as 'elastic' resistence to bending the hose. 3) If a nozzle is present and causes a pressure drop, or throttling, the increased turgor pressure also appears as an 'elastic' resistance to bending the hose. It's a puzzlement. Bill Maddux
