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General => General Technical Chat => Topic started by: GlennSprigg on August 21, 2019, 03:16:42 pm

Title: A Ship traversing a Water Canal like an Aquaduct ?
Post by: GlennSprigg on August 21, 2019, 03:16:42 pm
A friend of mine can NOT grasp this scenario...  Imagine there are 2 large lakes, with a Bridge
that is carrying water between the 2 lakes, like a large Aquaduct, with a tunneled road with
vertical piers underneath the 'Bridge'. (A 'road' goes under the water 'Bridge')......

Now imagine that in one of the lakes, there is a 20,000 Ton tanker/ship, that is moving to the
other lake. At one point, it is now stopped exactly in the middle of the 'water' bridge, with only
1-cm clearance on the sides & bottom.  Is there ANY extra weight on the Bridge???   NOPE!!   ;D

When the 'ship' was 1st put in the 1st lake, the water level had risen slightly across both lakes,
and the bridge. And a Floating Body displaces it's Own weight in water... So while being placed
on top of the bridge, it's water displacement is exactly equal to it's own weight....
So there is NO increase of weight on the bridge !!!  Physics 101 haha...   :palm:
Title: Re: A Ship traversing a Water Canal like an Aquaduct ?
Post by: ucanel on August 21, 2019, 03:24:06 pm
We do not have to imagine
there is a real one:

https://youtu.be/sFdpyxWcKwo
Title: Re: A Ship traversing a Water Canal like an Aquaduct ?
Post by: GlennSprigg on August 21, 2019, 03:40:48 pm
Quote from: ucanel on August 21, 2019, 03:24:06 pm
We do not have to imagine
there is a real one:

https://youtu.be/sFdpyxWcKwo

Thanks mate, I couldn't find a video to describe it !!!
Have a good day, from Aussieland to Turkey !!!
Title: Re: A Ship traversing a Water Canal like an Aquaduct ?
Post by: james_s on August 21, 2019, 03:45:35 pm
How is this not completely obvious? If the ship is there then the water that would normally occupy that space has moved somewhere else.
Title: Re: A Ship traversing a Water Canal like an Aquaduct ?
Post by: Mr. Scram on August 21, 2019, 03:46:10 pm
In larger bodies of water it becomes a bit more complicated as the differences in Earth's gravity cause seas to have actual hills and valleys of several meters tall. Those are hills made of water. Ships have to sail up hill. How about that?

https://indianapublicmedia.org/amomentofscience/hills-ocean/
Title: Re: A Ship traversing a Water Canal like an Aquaduct ?
Post by: Mr. Scram on August 21, 2019, 03:48:47 pm
Quote from: james_s on August 21, 2019, 03:45:35 pm
How is this not completely obvious? If the ship is there then the water that would normally occupy that space has moved somewhere else.
I don't think very many people can reproduce Archimedes' principle. It's a popular high school question because the intuitive answer tends to be the wrong one. Only when you know a floating object displaces its weight in water it starts making obvious sense.