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Specialty Chemistry Forums => Materials and Nanochemistry forum => Topic started by: o0CY0o on December 08, 2009, 11:10:59 PM

Title: About a man running on water.
Post by: o0CY0o on December 08, 2009, 11:10:59 PM
During my lecture, my professor gave me a challenging question which is about how come a fast moving car could run on water. He also illustrated this with videos on youtube.
He asked us to explain it from the point of view of material science and chemistry.
I think it is related to the creep relaxation in which it gives the time dependency to the water. Just like an ductile soft plastic will bounce well when it is thrown fast. i.e., short contact time.

Could anyone tell me wheather my idea is correct?
Title: Re: About a man running on water.
Post by: Borek on December 09, 2009, 03:49:52 AM
Not knowing video and not knowing what you exactly mean by "car runs on water" it seems question is unanswerable.
Title: Re: About a man running on water.
Post by: o0CY0o on December 09, 2009, 09:05:23 PM
Quote from: Borek on December 09, 2009, 03:49:52 AM
Not knowing video and not knowing what you exactly mean by "car runs on water" it seems question is unanswerable.

http://www.youtube.com/watch?v=apvJpZu1Ub0

This video..
sorry for the confusion
Title: Re: About a man running on water.
Post by: Borek on December 10, 2009, 03:21:57 AM
I think you are more or less right, water doesn't yield fast enough for the car to sink so it just skims on the surface. It is not much different from what so called "Jesus Lizard" does: http://www.youtube.com/watch?v=KSLUwmJOo_M (I remember an interesting article on these lizards in either National Geographic or Scientific American, not sure how precisely physics was explained).
Title: Re: About a man running on water.
Post by: o0CY0o on December 10, 2009, 11:47:27 AM
Quote from: Borek on December 10, 2009, 03:21:57 AM
I think you are more or less right, water doesn't yield fast enough for the car to sink so it just skims on the surface. It is not much different from what so called "Jesus Lizard" does: http://www.youtube.com/watch?v=KSLUwmJOo_M (I remember an interesting article on these lizards in either National Geographic or Scientific American, not sure how precisely physics was explained).

THanks for answering.
I want some maths. calculation on relationship between sigma (stress) and time.
As i think time dependence is the main concern.
Title: Re: About a man running on water.
Post by: PolymerKnowHow on December 10, 2009, 01:14:19 PM
For plastics, as you mentioned, I would read into time-temperature superposition. This explains, for example, silly putty.

Could the same concept apply for water?
Title: Re: About a man running on water.
Post by: o0CY0o on December 11, 2009, 08:10:47 AM
Quote from: PolymerKnowHow on December 10, 2009, 01:14:19 PM
For plastics, as you mentioned, I would read into time-temperature superposition. This explains, for example, silly putty.

Could the same concept apply for water?
I think it is using the time-tempreture superposition. However, i think this question focus on time. Also, I don't know how to do any calculation of the stress related to time. Could someone please help?