Fellow shadow watchers,
No doubt the following is well known but it came
as a surprise to me.
While filling a watering can with a garden hosepipe adjusted to give a
powerful single jet* I have to PUSH the hose firmly into the can to
overcome the reaction from the water jet BUT as soon as I dip the nozzle
into the water a smaller force takes over and seems to PULL it gently
down into the water. (no measurements made so purely subjective
conclusions)
i.e. the force reverses on entry!
Why is this so? and, if I'm right, how do 'jet' boats, working on the
reaction principle, function at all I wonder?
* 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.
Tony (should have paid more attention in Physics lessons) Moss
