## shubhamsrg How fast should one run on water so as to not sink? What parameters decide this ? one year ago one year ago

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1. shubhamsrg

2 obvious parameters are surface tension and weight Area of cross section in contact must also be one.

2. shubhamsrg

@Vincent-Lyon.Fr

3. Mashy

yea.. so .. if you are weight can be handled by surface tension.. then even if you stand on water you won't sink.."water strider is an example.. and even mosquito eggs".. However if the weight cannot be supported.. then even if you are run as fast as you can.. you will sink.. doesn't that seem logical?

4. shubhamsrg

Well I guess there is always a min speed for an object so that it doesnt sink. Take an example of pebble, you throw it and it may bounce of water , may even go for 2-3-4 or more bounces, ultimately it'll sink as the speed reduces.

5. gleem

the common Basilisk lizard also known as the Jesus lizard can run across a good stretch of water while keeping most of its body above the surface see en.wikipedia.org/wiki/Common_basilisk for a video and explanation of how it does this. I don't think it is in the ability of a human to do this.

6. Mashy

hmmm yea shubhamsrg.. i think i stand corrected.. there must be a min speed.. maynot be possible for us to do it. but theoretically we must be able to work out a min. speed!!

7. DLS

$\LARGE V>3 \times 10^8m/s$

8. DLS
9. jrod326

no clue|dw:1361556181730:dw|

10. experimentX

For the pebble, i guess it's due to Bernoulli's principle ... for one side you have much denser water and other side you have air ... besides you add spin to the pebble for it to bounce. For human, i guess you have kick hard ...

11. DLS

or sit in a cannon and shoot yourself with escape velocity

12. experimentX

@DLS you can't reach that speed 3x10E8 ,,, that's relativistically impossible ... although hypothetical particles called Tachyons were believed to reach greater that c. You don't need esc velocity ... just find velocity that keeps satellite rotating.

13. shubhamsrg

I guess someone has written about a book on my ques, am not too sure, I have just heard. :|

14. shubhamsrg

I was wondering if that can be calculated considering , foot size, mass, surface tension, etc

15. experimentX

this is pretty interesting topic ... there must be some!!

16. DLS

@experimentX how do you know about stuff like Tachyon :O sugoi!

17. experimentX

lol ... I think this or something like it http://en.wikipedia.org/wiki/Journey_to_the_Center_of_the_Earth_(2008_Hollywood_film)

18. johnniewalker

You also need to include a buoyant force when calculating the speed required as it will reduce the needed speed.

19. RaGhavv

can viscosity play a thing in deciding that..?

20. shubhamsrg

I'd say yes.

21. asmagul

fast enough so that your feet dont sink through the initial surface tension and so that your step is quick enough not to displace water going by famous 'jesus lizards' who are 200 grams as adults they run at 1.5 metres per sec over water in proportion a human (about my size) at 12-13 stone would have to run at about 60-70 metres per sec (yes!) which is about 250 kilometres per hour

22. RaGhavv

i am not sure on this but still... normally when athletes run on land,,then their area of of contact is quite less..i mean we can also realise when we are racing or walking fast... and the rate with which their feet touches the ground is also quite high... now consider the picture of water..let us assume that when we are running on it,,a tiny film of water is formed between our feet and the corresponding layer of water..and so when we are running ,we are pushing that film of water backwards..which is in contact with the other layers of water.. so then we can say that viscosity is playing its part... and $\eta=Fl/vA...or v=Fl/\eta A$...so here are its parameters if my assumption is true...and it means we have to gain speed according to our weights bcoz the area of film would be more or less the same..

23. kt.venkatesan

You can’t run on water without sink with bare foot. You will feel like running on the surface of water when you’re running fast enough from ground to surface of water. It happens because of the inertia of our body. It can happen in the air also, if you try to run fast enough from a place above from ground level. The difference is because of the air and water resistance towards the gravitational force.

24. chenping

cool.. Basically running on the same spot is an impossiblity since the water won't move the way against ur running direction. But I do believe that a human can run across the water (river usually..) There's been tales about some ancient monks (eg: Bodhidharma, the founder of ShaoLin) can perform this act. If we train for the same thing ever and ever again till we die, will our next few generations (who must do the same too) evolved to adapt to run on water? :P