Was checking out facebook today and this viral video caught my eye. It's amazing how a bit of simple physics gets so much interest, over 3 million views on youtube and over 9 on facebook. When I first saw the video I thought that the timing would have to be very precise for it to work so I made some measurements to see how it was, The time period of the swing is about 4s so the rope length is 4m (seems about right). The water takes 0.9s to fall the length of the rope. The water turns off as the swinger gets to the top of the swing and on again just before they get to the middle, 1s later, so the water has cleared from the trajectory and has not enough time to make it down onto their head, this pattern is repeated. So, if the amplitude was less would they get wet. Well, the time period won't change but their velocity as they swing through the equilibrium position will get smaller so they spend more time in the danger area. This is probably why the people stepped in to remove the swingers from the swing.

A secondary interesting aspect is the parabolic shape of the water in the photo, it seems that the water at the edges gets released before the water in the middle. If the time delay between the jets was constant then that would lead to a parabolic shape. I wonder what the mechanism looks like.

I tried fitting a parabola to the photo (in LoggerPro) but it wasn't a good fit due to the perspective of the photo. Would be interesting to work out how to correct for that.

Here is how it works: waterfall swing. It's a bit more complex than I had imagined, I thought it would be mechanical.

This sort of thing would make a great topic for an investigation.