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They sink after running for 20 feet because with each step they are getting less return force from the surface of the water. At some point the next step will pl

They sink after running for 20 feet because with each step they are getting less return force from the surface of the water. At some point the next step will plunge through the surface and they will sink just as quickly as if their first step was not at a run and not with high and quick knee lifting.

ck2 16y ago
Plain water is not a dilatant. Skipping a stone or snowmobile is not the same forces in effect as stepping on water at less than 12mph with the tiny surface area of a human foot. There is something very suspect with this whole video.
- Nwallins 16y ago
  I don't know what a dilantant is, but in order for a human to maintain a high speed, he is pushing -- nay, driving -- his feet into the running surface. Water does not provide this level of resistance for something with a high psi such as a human foot.
- krschultz 16y ago
  It's a questions of surface tension of the water. I'd have to think about the physics a bit, but if you fall wakeboarding, you can skip across the surface of the water for a good ways (done it). Considering your max speed is about 20 mph, and when you fall you immediately let go of the rope and decelerate rapidly, I would say a human body can skip across the water at roughly 15 mph. It is entirely dependent on you though, if you let anything pierce the surface it's over. If you make sure your limbs stay up then you can skip a few times. I'm still pretty sure this is a hoax but I bet you could do what they are doing if you could move feet fast enough (which may be impossible for a human, but a machine with feet that moved faster might be able to). Water has surface tension no matter what the speed, you just need to get out of the hole created faster than you fall through it.
  - ck2 16y ago
    Wasn't there a Mythbusters episode about this and it was busted? Something about how ninjas in movies walk across water. They tried to make their feet pontoons but it was hopeless. Ah, here it is http://www.youtube.com/watch_popup?v=5GWhOLorDtw http://www.youtube.com/watch_popup?v=5GWhOLorDtw
    - jodrellblank 16y ago
      If we assume Ninjas can walk across water, we can also assume it's going to be something they learn in the years of training where they go from ordinary person to ninja. Two ordinary people trying for a few hours wouldn't be enough to pronounce it an impossible feat, it would just say that ordinary people can't walk accross water without years of ninja training - and we know that bit already!
    - Tamerlin 16y ago
      In a manner of speaking, they COULD walk across water... by cheating: they used lily pads. Big ones. It was like wearing rafts. After that, it was just a matter of learning to choose the right lily pads, being careful, and keeping your balance. Nothing supernatural or anything like that, just learning to take advantage of what nature has on offer :)
  - something 16y ago
    i don't think surface tension is doing anything for something the size of a human, or a stone for that matter. if it was surface tension, why does it care that something is moving? it probably has more todo with the water you are displacing having enough inertia that it can't get out of your way fast enough. it stays there long enough to deflect your path upward, keeping you up. you sink when you pierce the surface because of the massive drag you introduce. it slows you down very quickly so you sink.

ck2 16y ago

Plain water is not a dilatant. Skipping a stone or snowmobile is not the same forces in effect as stepping on water at less than 12mph with the tiny surface area of a human foot. There is something very suspect with this whole video.

Nwallins 16y ago
I don't know what a dilantant is, but in order for a human to maintain a high speed, he is pushing -- nay, driving -- his feet into the running surface. Water does not provide this level of resistance for something with a high psi such as a human foot.
krschultz 16y ago
It's a questions of surface tension of the water. I'd have to think about the physics a bit, but if you fall wakeboarding, you can skip across the surface of the water for a good ways (done it). Considering your max speed is about 20 mph, and when you fall you immediately let go of the rope and decelerate rapidly, I would say a human body can skip across the water at roughly 15 mph. It is entirely dependent on you though, if you let anything pierce the surface it's over. If you make sure your limbs stay up then you can skip a few times. I'm still pretty sure this is a hoax but I bet you could do what they are doing if you could move feet fast enough (which may be impossible for a human, but a machine with feet that moved faster might be able to). Water has surface tension no matter what the speed, you just need to get out of the hole created faster than you fall through it.
- ck2 16y ago
  Wasn't there a Mythbusters episode about this and it was busted? Something about how ninjas in movies walk across water. They tried to make their feet pontoons but it was hopeless. Ah, here it is http://www.youtube.com/watch_popup?v=5GWhOLorDtw http://www.youtube.com/watch_popup?v=5GWhOLorDtw
  - jodrellblank 16y ago
    If we assume Ninjas can walk across water, we can also assume it's going to be something they learn in the years of training where they go from ordinary person to ninja. Two ordinary people trying for a few hours wouldn't be enough to pronounce it an impossible feat, it would just say that ordinary people can't walk accross water without years of ninja training - and we know that bit already!
  - Tamerlin 16y ago
    In a manner of speaking, they COULD walk across water... by cheating: they used lily pads. Big ones. It was like wearing rafts. After that, it was just a matter of learning to choose the right lily pads, being careful, and keeping your balance. Nothing supernatural or anything like that, just learning to take advantage of what nature has on offer :)
- something 16y ago
  i don't think surface tension is doing anything for something the size of a human, or a stone for that matter. if it was surface tension, why does it care that something is moving? it probably has more todo with the water you are displacing having enough inertia that it can't get out of your way fast enough. it stays there long enough to deflect your path upward, keeping you up. you sink when you pierce the surface because of the massive drag you introduce. it slows you down very quickly so you sink.